How to use two SIM cards in Galaxy S8 and S8+?

Dual SIM version Galaxy S8 and S8+ allows you to use two SIM cards in the phone. Although Galaxy S8 and S8+ are dual standby only, you can use dual SIM always on and will not miss any calls.

This Galaxy S8 guide explains the limitations of using two SIM cards in Galaxy S8 and S8+, how to use and customize dual SIM card settings, how to enable dual SIM always on to avoid missing calls.

When you can use two SIM cards in Galaxy S8 and S8+?

In many international markets, Samsung released dual SIM version of Galaxy S8 and Galaxy S8+.

For these dual SIM Galaxy S8 and S8+, you can use up to 2 SIM cards. Of course, they are dual standby only, not dual active because there is one modem shared by two SIM cards.

You can use two SIM cards only in dual SIM version of Galaxy S8 and S8+.

As explained in the Galaxy S8 SIM card guide, the SIM card tray for single SIM and dual SIM version of S8 and S8+ is different.

But the difference is not only in the SIM card slot. The firmware (software) is also different.

In addition, the metal contact part inside the phone is also different in dual SIM version and single SIM version of Galaxy S8 and S8+.

So, there is no easy way to convert single SIM version of Galaxy S8 or S8+ to dual SIM version. Don’t waste time and money on this.

What are the limitations of using two SIM cards in Galaxy S8 and S8+?

As dual SIM version of Galaxy S8 or S8+ is dual standby only. In theory, two SIM cards are both active only when the phone is in standby.

This means you can receive and make calls on both SIM cards, but not concurrently.

When you are engaged in a call with one SIM card, the other SIM card by default will be unreachable.

However, you can set call forwarding from one SIM card to the other one, and enabling call waiting to get “dual SIM always on” (read on).

In short, the limitations of using two SIM cards in Galaxy S8 and S8+ include:

• You cannot use micro SD card.
• Dual standby only;
• Only one SIM card can be assigned to use mobile data. By default, it is SIM card 1.
• Most carriers will charge call forwarding minutes if you want to make both SIM cards available at any time even when you are engaged in a call.
• Dual SIM always on may be not available in a few carriers’ networks who do not support call waiting (call holding).
• Mobile data speed may be affected when using two SIM cards.
• Battery life may be affected depending on signal strength and quality.

How to use two SIM cards in Galaxy S8 and S8+?

As explained in Galaxy S8 SIM card, you can put two SIM cards in the SIM card tray.

Because slot 2 is for either a SIM card or a SD card, you will not be able to use micro SD card when using two SIM cards in Galaxy S8 and S8+.

You just need follow the guide to put two SIM cards in the tray and they should be recognized after you power on your Galaxy S8 or S8+.

Although it is not required, you should power off Galaxy S8 and S8+ before adding or replacing SIM card.

How to know whether you are using two SIM cards in Galaxy S8 and S8+?

If both of the two SIM cards are working, you will find some additional status icons as shown below.

For example, as shown below, you can find two signal strength bar (marked as 2 and 3 in the screenshot), instead of 1.

SIM card 1 icon (marked as 1) indicates mobile data is activated on this SIM card.

In addition to the icons in status bar, you can also find the difference in notification shade.

As shown below, when you use two SIM cards in Galaxy S8 and S8+,  under the quick settings bar, you can find the default SIM card info.

In this example, SIM card 1 was chosen as the default SIM card for outgoing calls and messages.  Mobile data was also enabled in SIM card 1.

How to customize SIM card settings for two SIM cards in Galaxy S8 and S8+?

You can customize SIM card settings for the two SIM cards in Settings —Connections — SIM card manager.

As shown below, in SIM card manager, under general settings, you can input the number for SIM card 1 (marked as 4 in the screenshot) and SIM card 2 (marked as 5).

If you want, you can just leave it as unknown. This should not affect any functions.

Under Preferred SIM card, you can set the default (preferred) SIM card for calls (marked as 6), text messages (marked as 7) and mobile data (marked as 8).

By default, SIM card 1 (in slot 1) is set as the preferred SIM card for all activities.

You can tap each of these three fields to set it as:

• SIM 1; or
• SIM 2; or
• Always ask.

You should set them up based on your usage preference.

Please note, in Galaxy S8 and S8+, the Phone app (dialer), you can always choose SIM card before placing calls.

As shown below, you can tap the phone icon with number 1 to use SIM card 1, or phone icon with 2 to use SIM card 2, regardless of the SIM card preference settings.

This is Samsung’s customization. In other Android phones, you may not have this option.

Similarly, in call log (history tab), you can also choose SIM card to call back.

But for text messages, the default preferred SIM card setting will be used.

Under call settings as shown above, you can:

• Enable or disable confirm SIM card for calls (marked as 9). When you use the non-preferred SIM card for outgoing calls, you can choose to confirm the choice before the call is placed. This is useful when one SIM card is roaming, and the other is local.
• Enable or disable dual SIM always on (marked as 10, read on).

How to set up and use dual SIM always on in Galaxy S8 and S8+?

As mentioned earlier, dual SIM version of Galaxy S8 or S8+ is dual standby only.

For dual standby dual SIM phones, by default, when you are engaged in a call, the other SIM card will not be reachable.

This means you may miss some calls.

Thankfully, Galaxy S8 and S8+ give you the option to make both SIM cards reachable at all times.

You just need to enable dual SIM always on (marked as 10).

The dual SIM always on requires two mobile network features:

1. call waiting (call hold); and
2. call forwarding (call diversion).

Most of the carriers support these features.

But call forwarding is not free. Your carrier will very likely charge it as the outgoing minutes.

So do not use dual SIM always on when one SIM card is roaming.

When you enable dual SIM always on the first time, you will be asked to input the phone numbers of SIM card 1 and SIM card 2 as shown below.

Please make sure the number is correct for the corresponding SIM cards.

After you provide the phone numbers, you can then choose to use dual SIM always on in 3 configurations:

1. Both SIM cards. You want to make both SIM cards available for callers at all times. You will not miss any calls.
2. SIM card 1 to SIM card 2.  SIM card 1 will be available for callers at all times. But you may miss calls to SIM card 2 (when you are engaged in calls in SIM card 1).
3. SIM card 2 to SIM card 1. This is opposite to option 2. You may miss calls to SIM card 1.

The default option is both SIM cards.

You should choose the option based on your needs. You should also factor in possible call forwarding charges.

Once you tap finish, Galaxy S8 and S8+ will write corresponding settings to each SIM card as shown above.

Please note, this works on most (not all) SIM cards.

It also may take about 1 to 3 minutes to update the settings to SIM card.

Once the settings are successfully written to the SIM card, you will get a pop up messages informing you what settings were updated as shown above:

Dual SIM always on

SIM card 1: SIM card 2 call waiting enabled. If SIM card 1 is out of reach, incoming calls will be forwarded to XXX (SIM card 2 number).

SIM card 2: SIM card 1 call waiting enabled. If SIM card 2 is out of reach, incoming calls will be forwarded to XXX (SIM card 1 number).

Tap OK to exit the settings.

If you want to manually set call forwarding and call waiting for each SIM cards, you can do so in Phone app.

How to check and fix problems related to using dual SIM cards in Galaxy S8 and S8+?

If you have any issues when using two SIM cards in Galaxy S8 and S8+, you may first check the SIM card status to gather some diagnostic info.

In Settings —About phone, tap status as shown below.

In status page, tap SIM card status as shown below.

In SIM card status page, you can find two tabs: one for SIM 1 and the other for SIM 2.

You can check the mobile network info including:

• Network. This should be your carrier’s network name.
• Signal strength.
• Mobile network type.
• Service state.
• Roaming.
• Mobile network state. This is the mobile data connection status. It is connected only when data are transferred.

Do you know how to use two SIM cards in Galaxy S8 and S8+? Can you set dual SIM always on?

If you have any questions or encounter any issues with using two SIM cards in Galaxy S8 and Galaxy S8+, please let us know them in the comment box below.

The community will help you find the answer or solution.

You may also check our Galaxy S8 guides:

• Galaxy S8 new features guide covers all new and unique features of Galaxy S8 and S8+.
• Galaxy S8 how-to guides give you detailed step-by-step guides on using most features of Galaxy S8 and S8+.
• Galaxy S8 user manuals lets you download official Samsung Galaxy S8 user manuals in your won language.
• Galaxy S8 camera guides covered everything related to Galaxy S8 camera is covered in Galaxy S8 camera guides section.
• Galaxy S8 accessories guides help you find the perfect accessories for Galaxy S8 and S8+.

In addition to post your thought or questions in the comment box below, you can also reach us in Facebook page.

Don’t forget to subscribe to our free newsletter!

Subscribe to our free Galaxy S8 tips, tricks and guides newsletter to get the most for your Samsung Galaxy S8 and S8+!