Many new smartphones nowadays come with dual-SIM capability and have an eSIM in addition to the physical SIM slot. With the eSIM technology, the SIM hardware (chipset) is already built inside the phone, which you can programme digitally using a QR code from your mobile operator (carrier).
An unlocked dual SIM phone can work with two SIMs from any mobile network or carrier to give you two separate SIM plans and phone numbers. If you have a dual SIM phone with an eSIM and a physical SIM, you can use SIMs from two different networks even if one of the SIMs is from another country.
Only an unlocked dual SIM phone can be on different networks
If you want to use your dual SIM phone on two different networks, your phone must be unlocked. An unlocked mobile phone can handle any compatible SIM card from any mobile network operator. However, the SIM must belong to a mobile network using a cellular technology (e.g. GSM, UMTS, LTE) supported by the phone.
So if you have a dual SIM phone with an eSIM and a physical SIM, the phone needs to be unlocked so that you can use it with SIMs from two different mobile network operators. When you buy a mobile phone through a mobile operator, it is possible that the phone may be locked to their network. If your phone has a network lock, it will only work with the SIM from the carrier (mobile operator) whose network your phone is locked to.
The best way to check if your phone has a network lock is to simply insert a SIM card from a mobile network operator that is different from the one whose SIM you currently have in your phone. A phone that is locked to a specific network will not allow you to access any other mobile network. However, if after inserting the SIM, you see the signal bars and you can dial a phone number, then your phone is unlocked.
Using your eSIM and regular SIM to access different networks
If you have an eSIM-enabled smartphone, it is likely that it may have dual SIM capability allowing you to use an eSIM and a physical SIM. You can check the specifications for your phone by contacting the phone manufacturer or your mobile operator. You can also check that directly on the GSM Arena’s website where you can enter or select your phone model to see the detailed specifications.
We are using a Google Pixel 5 phone to show you how you can place two SIMs from different mobile operators to utilise the eSIM and physical SIM in a dual-SIM phone. That way, you can have two different phone numbers on the same phone without needing two physical SIM cards. We are also using SIMs from three different mobile network operators (MNOs) in the UK: Vodafone UK, O2 UK and EE.
On our Google Pixel 5 phone, we first downloaded and activated an eSIM from Vodafone UK. If you want to know how to use an eSIM on your phone, please check out my dedicated post on how to download an eSIM on iPhone and Android phones.
We then inserted the SIM cards from O2 and EE, one at a time, into the physical SIM slot of our Google Pixel phone. If you look at the screenshots below, you can see that the Vodafone UK eSIM is showing there as SIM # 2, whereas the plastic SIMs from O2 (the left screenshot) and EE (the right screenshot) are showing as SIM # 1.
You need to choose a default SIM for mobile data (internet)
As soon as you put the second SIM in a dual-SIM phone, it asks you to choose the default SIM for mobile data (mobile internet). In our example, the screenshots above show how a Google Pixel 5 phone displays the “Select a SIM for data” screen when the second SIM is inserted.
One of the key benefits of a dual SIM phone, irrespective of whether it uses an eSIM or physical SIMs, is that it enables you to separate your data from calls and texts by using a different SIM for mobile data. That way, when you travel abroad, you have the option to purchase a local prepaid SIM with enough data so that you can turn off the mobile data on your primary SIM to avoid data-roaming charges.
But, of course, if you want to make or receive regular phone calls through your primary SIM or send text messages, all the calls and texts may be subject to roaming charges depending on which countries you visit.
If you purchase a local SIM for your dual-SIM phone to cover your data needs in the country you are visiting, you can avoid the expensive data-roaming costs while still being able to use all the apps on your phone including WhatsApp. Having a local SIM for mobile data allows you to use your main WhatsApp account (linked to your main number) on international trips without having to look for free Wi-Fi hotspots.
In the example below, we are using a data-only SIM from O2 UK in our Google Pixel 5 dual-SIM phone for our mobile data needs. The Vodafone UK SIM (eSIM) is set to calls and texts only. However, if someone calls our WhatsApp account linked to the Vodafone UK number or if we want to call someone on WhatsApp, we can still make and receive WhatsApp calls using mobile internet enabled by the O2 UK SIM.
You can select the default SIMs for calls and texts (SMS)
Once you have set the default SIM for mobile data, you can also choose your preferred SIM options for voice calls and text messages (SMS). In our example with the Vodafone UK and O2 SIMs in the Google Pixel phone, the “Calls and SMS” menu allows you to choose the preferred SIM for making calls and sending text messages.
As you can see in the screenshots below, the “Calls and SMS” menu in the Google Pixel phone gives you the option to either choose the preferred SIM or set it to “Ask every time”. Unlike mobile data, where the default setting must be used unless you change that in the phone settings, with phone calls and text messages it is possible to choose the relevant SIM for each call and text.
You can opt to select the right SIM before making each call
Depending on your preference, you may decide not to use a default SIM for phone calls. If you do not set a default SIM for making calls, you will be asked by the phone to choose the appropriate SIM each time you attempt to make a phone call.
In our example, we have set our Google Pixel phone setting to “Ask every time” so that it asks us to choose the correct SIM before making each call. As shown in the screenshot below, when calling our friend Mark from this phone, the phone asks us if we want to use the O2 SIM or the Vodafone UK SIM to make the call.
You can also choose the preferred SIM when sending each text
When sending text messages through a dual-SIM phone, you have the option to choose the preferred SIM for each text message. If you have a default SIM for text messages (SMS), that SIM will be automatically selected as the sender of the text unless you change that before sending the text.
The default SIM for text messages (SMS) will appear as an icon in the text message area where you compose the message. When you tap on that icon, it allows you to switch between the SIMs. In our example below, if you tap on the SIM icon in the left screenshot, a new screen pops up that allows you to change your SIM selection.
Once you have sent the text message after selecting the appropriate SIM, depending on your phone manufacturer, you may be able to see which SIM sent the message by simply tapping on the message.
For example, if you look at the screenshot below, you may note that our Google Pixel 5 phone can identify the SIM that sent the message. So, when we tapped on the two “Hello” messages sent by us, the phone displayed which message was sent by the Vodafone SIM and which message was sent by the O2 SIM.
People can call you on any of the two SIMs
Receiving a phone call on a dual SIM phone is very straightforward. When someone calls you on either of your two SIMs in a dual-SIM phone, you see a notification on your phone screen about the incoming call. The notification also tells you which SIM the call is for.
However, since most eSIM-enabled dual-SIM phones belong to the Dual SIM Dual Standby (DSDS) category, you can only take one call at a time. Therefore, during your call, if someone tries to call you on the other SIM, they will not be able to reach you and may get directed to your voicemail if you have that service from your service provider.
As you can see in our example below, when our friend Mark calls us on any of the two SIMs on our dual-SIM phone, the notification tells us which SIM the call is for.
People can text you on any of the two SIMs at any time
For the people who send you text messages, your two SIMs are like two separate phones. Since each SIM has a different phone number, your contacts will need to send the text messages separately to each number.
When you receive the text messages from your contacts, all the texts from a particular person will show on the same text message screen on your phone, irrespective of which of your SIMs they send the message to. So, for example, in the screenshot below, our friend Mark sent the “Hi” message to both our Vodafone UK and O2 SIMs, and both messages are displayed on the same screen.
You can use your eSIM to have an additional SIM plan
One of the challenges with an eSIM-enabled dual SIM phone in the UK is that currently, eSIM is only available on pay-monthly tariffs (postpaid) and not on the pay-as-you-go tariffs (prepaid). So if you are already using your physical SIM slot for a pay-monthly SIM, you may need another pay-monthly subscription to be able to utilise the eSIM capability on your phone. I have written a dedicated post that explains the difference between prepaid and postpaid subscriptions.
If you want to avoid paying for two pay-monthly subscriptions, you can move your existing pay-monthly (postpaid) subscription to an eSIM to free up your physical SIM slot. By freeing up your physical SIM slot, you get more choice when buying an occasional prepaid SIM for your phone to enjoy the dual-SIM experience.