The dual-SIM version of Galaxy S10 can work in dual-standby mode. The two SIM cards share (time-sharing) one modem and therefore the dual SIM version of Galaxy S10 does not support dual active mode.
This Galaxy S10 how-to guide explains how to use two SIM cards on Galaxy S10, S10+, S10e, S20, S20+, and S20 Ultra, how to enable and use dual SIM always on and how to use SIM card manager to set preferred SIM cards for calls, messages, and mobile data.
Please note, Galaxy S10 5G only supports one SIM card in all regions. So, in this guide, Galaxy S10 refers to Galaxy S10, S10e, and S10+ only.
Galaxy S20, S20+, and S20 Ultra (both 5G and 4G variants) have a dua-SIM version. You can also use two SIM cards on these phones. This guide also applies to these Galaxy S20 phones as well.
Who can use two SIM cards on Galaxy S10, S10+, S10e, S20, S20+, and S20 Ultra?
In most regions of Europe, Asia, Oceania, Africa, the Middle East, and Latin America, Galaxy S10 (except S10 5G) supports two SIM cards (dual SIM version).
You can use two SIM cards concurrently. In some countries, some carriers charge excessively for mobile data if the SIM card can also make calls. Some bundle very limited mobile data with voice plans. In this case, you can use one SIM card for calls, one for mobile data.
Or when travelling, you can use one SIM card issued in your home country and the other one from a local carrier. In this way will not miss important calls and messages without paying excessive roaming voice and data fees.
You can also use one SIM card for work-related communications, and the other for private affairs.
To use two SIM cards on Galaxy S10, you need to have a dual SIM version of Galaxy S10. As mentioned, unless you bought Galaxy S10 in North America, your Galaxy S10 (S10, S10+, and S10e) is very likely the dual SIM version.
How to check whether the Galaxy S10 is a dual SIM version or a single SIM version?
If you are not sure, check the IMEI number in Galaxy S10 Settings —About phone.
Also, if the model number has a suffix of /DS as shown in the screenshot, it also indicates it is a dual SIM version of Galaxy S10.
Of course, on the box of Galaxy S10, the dual SIM version is usually stated as Duos.
The limitations of Galaxy S10 dual SIM capabilities
For dual SIM phones, there are two variants: dual standby, and dual active, as explained in this guide.
In a nutshell, dual-SIM dual-standby (DSDS) means the two SIM cards share one set of modem and antenna. The time-sharing (similar to virtualization) is implemented in the software, and the user should not notice it when both SIM cards are in the standby mode, or neither of them is engaged in voice calls.
While dual SIM dual active (DSDA) means there are two sets of modem and antenna. So two SIM cards work independently.
Due to improvements in DSDS, and the lower cost of implementing DSDS, none of the major Android manufacturers has released any DSDA Android phones in the last 3 to 4 years.
Obviously, the dual SIM version of Galaxy S10 is dual standby (DSDS) only.
Therefore, you will encounter the following limitations when using two SIM cards on Galaxy S10:
- Dual standby only.
- When a SIM card is engaged in a voice call, or using 2G mobile data, you must enable dual SIM always on (call forwarding and call waiting for the SIM cards) in the SIM card manager. Otherwise, the other SIM card will not be reachable if someone calls this number.
- You will not be able to use a micro SD card. The slot 2 in the Galaxy S10 SIM card tray can only hold one card: a SIM card OR a micro SD card, not both, at any time. For Galaxy S20, Galaxy S20+, and Galaxy S20 Ultra, if your carrier supports eSIM on Galaxy S20, then you can free up the slot 2 and therefore use two SIM cards (one physical and one eSIM) and one micro SD card concurrently as explained here.
- Nano SIM cards only. Both slots in the SIM card tray can only hold nano-SIM cards although slot 2 looks larger.
Please note, both SIM cards have equal access to all apps and data. If you need to use two copies of the messaging apps or social network apps, you should enable the Dual Messenger.
You do NOT need to use two SIM cards on Galaxy S10 if you want to use Dual Messenger as long as you can log in the messaging app with your credentials.
How to insert two SIM cards on Galaxy S10?
As explained in the Galaxy S10 SIM card guide, the slot 2 of the Galaxy S10 SIM card tray on the dual SIM version of Galaxy S10 can hold a nano-SIM card or a micro SD card.
If you decide to use two SIM cards on Galaxy S10 temporally or in the long period, you have to remove the SD card.
As illustrated below, you will use option 1, and you need to put one SIM card in slot 1 in the SIM card tray and the other one in slot 2.
In this case, the slot number does NOT matter. There is no primary or secondary slot for SIM cards when using two SIM cards.
Again, if you want to use the micro SD card, you will have to use option 2, and you will not be able to use two SIM cards.
Please refer to Galaxy S10 SIM card guide on how to eject the SIM card tray, put or replace SIM cards on Galaxy S10.
How to use Galaxy S10 SIM card manager?
When using two SIM cards on Galaxy S10, you will need to use the SIM card manager to customize some functions and features.
You can access the SIM card manager in Settings — Connections.
In Galaxy S10 SIM card manager, you can:
- Customize the icon, name and network type for each SIM card.
- Set the preferred SIM card for voice calls, text messages, and mobile data.
- Tweak the call settings.
For example, if you want to customize SIM card one, tap SIM 1 (default name for SIM card in slot 1) as shown above (marked as 1)
In the SIM 1 page, as shown below you can:
- Disable or enable this SIM card.
- Change the icon for this SIM card. You can choose one from the pre-installed icons for the SIM card.
- Set the name for this SIM card. You can name it as you want.
- Set network mode for this SIM card. You seldom should change this. Auto connect (the default) is usually the best option.
You can do this similarly to customize SIM card 2.
You can also set the preferred (default) SIM card for voice calls, text messages and mobile data.
On the dialer of the phone app and the Messages app, you actually have two buttons marked as “1” and “2” for you to choose when placing calls or sending messages. The preferred SIM card settings here are for third-party apps that may bypass the interface.
As shown above, you can set preferred voice calls to SIM 1, SIM 2, or Ask always.
For mobile data, you can choose one SIM card for mobile data, or disable mobile data (which can also be done using the mobile data button in Galaxy S10 quick settings panel).
Although Galaxy S10 is sometimes marketed as dual 4G (i.e., both SIM cards can connect to 4G LTE network concurrently), only one SIM card (which you assigned here) will be used for mobile data. The other will only be used for voice and messages.
What is dual SIM always on? How to set up dual SIM always on for Galaxy S10?
By default, when you are talking through one SIM card, the other SIM card will not be reachable. So, if someone calls you this unreachable SIM card, he will get an unreachable (instead of busy) notification, and you will not get any notification. You may miss some important calls.
To solve this issue and make both SIM cards reachable at all times (even when you are talking on one SIM card), you need to:
- Enable call forwarding when unreachable for both SIM cards.
- And enable call waiting for both SIM cards.
Some carriers may name call forwarding as call divert. Almost all carriers support call forwarding.
Once you finish these settings, when you are talking on SIM card 1, and someone is calling you to SIM card 2, you will get the notification for the incoming calls to SIM card 2. If you pick up the second call, the first call will be on hold.
On Galaxy S10, Samsung made it simple for you to configure this and name it as dual SIM always on. (FYI, you can follow this guide to manually set up call forwarding and call waiting for each SIM card in the phone app as in other Android phones.)
On the SIM card manager shown earlier, you can tap dual SIM always on (marked as 3), then Galaxy S10 will try to set up call forwarding and call waiting for you automatically for you.
As shown in the screenshot below, Galaxy S10 will ask you to confirm whether you want to use this feature:
Turn on dual SIM always on
Turn on dual SIM always on? (with some service providers, this function may not work properly or you may be charged)
Tap OK to processed.
Now, as shown above, you need input the number associated with the two SIM cards.
It looks silly because many owners assume the phone knows your numbers. This is not the case. Your number can be changed on-the-fly by your carrier without changing the SIM card.
Normally, Galaxy S10 knows the IMSI (International mobile subscriber identity) number, which is unique to each SIM card and is always saved in the SIM card. But the MSISDN (mobile subscriber integrated services digital network ) number, which includes your phone number, may or may not be saved in the SIM card. The carrier can change this at any time from their side once the SIM card is registered on the network.
Anyway, you need to manually input the phone numbers as shown below.
Tap Next after entering the phone numbers.
As shown above, you now choose whether the call forwarding is two-way or one-way.
If you want to make sure both SIM cards are reachable, you need to choose Forward calls to any SIM.
If you choose one-way forwarding, only one SIM card will be always reachable.
You should not worry about infinite forwarding loop (SIM 1–> SIM2 –>SIM 1–>…). All carriers will prevent this happen because they will divert calls only once.
Tap Done as shown above to finish the setting.
It will take up to a few minutes (depending on your mobile signal strength and quality) to finish the configuration because all these settings need to be done on your carrier's servers, not just on the phone.
You should wait.
Once it is done, you will get the confirmation as shown in the screenshot below.
You can disable dual SIM always on at any time by tapping dual SIM always on (marked as 3 as shown earlier) in the SIM card manager, then tap the On button to change it to off as shown above.
Again, it will take one or two minutes.
After you use the dual SIM always on once, there will be a dedicated page for dual SIM always on as shown above even you turn it off later.
When should you disable dual SIM always on?
Dual SIM always on is NOT for all owners.
Although almost all carriers offer call forwarding (divert) as a free feature, they normally charge you for the forwarding.
For example, you use dual SIM always on to forward calls to SIM 1 to SIM 2. When you pick up the forwarded call, carrier 1 will charge you for outgoing minutes and carrier 2 will charge you for incoming minutes.
So, if you are using two SIM cards on Galaxy S10 with one international roaming card, the call forwarding charge can be very high.
Anyway, you need to check your mobile plan and your carrier charges before enabling dual SIM always on.
Can I convert a single SIM version of Galaxy S10 to dual SIM one?
No, you cannot.
The difference between the single SIM version of Galaxy S10 and the dual SIM version is not just the SIM card tray.
Both hardware and software are different for the single SIM and dual SIM versions. There is no “reader” for the second SIM card on a single SIM version of Galaxy S10.
Can I use a micro SD card together with two SIM cards on Galaxy S10?
No, you cannot use a micro SD card together with two SIM cards on Galaxy S10.
Do NOT follow such guides. You may end up buying a new Galaxy S10.
Do you know how to use two SIM cards on Galaxy S10, S10+, and S10e? Do you know how to set up and use dual SIM always on? Can you use the SIM card manager to customize the SIM cards on Galaxy S10, S10+, and S10e?
If you have any questions on using two SIM cards on Galaxy S10, S10+, and S10e, please let us know in the comment box below.
The community will help you find the answer.
If you have questions on new features of Samsung Galaxy S10, please check Galaxy S10 new features guides page.
For using Galaxy S10, please check Galaxy S10 how-to guides page.
You can find the detailed guides of using Galaxy S1o camera in Galaxy S10 camera guides page.
To find and use accessories for Galaxy S10, please check Galaxy S10 accessories guides page.
To read and download the official Samsung Galaxy S10 user guides (in PDF format) in your local language, please check Galaxy S10 user guides page.
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