Dual-SIM with eSIM: Complete FAQ Guide

With eSIM, true dual-SIM functionality is finally a reality.

Dual-SIM phones have been around since 2000 when Finnish telecommunications company, Benefon (now TWIG), released the 2G Benefon Twin+ with two SIM slots.

But it was not what we now know it to be.

The earliest dual-SIM phones required a clumsy adapter, which thankfully became obsolete with later adaptations. Things got simpler but it wasn’t really until eSIM phones hit the market that people really started appreciating the advantages of dual-SIM.

This post examines what dual-SIM is and how the development of embedded SIM technology has helped dual-SIM phones reach their full potential.

Related | Three Reasons Why You Should Buy an eSIM

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man holding dual-SIM phone

What is the Point of a Dual-SIM Phone?

Dual-SIM phones allow mobile users to have two SIM cards on one device. But why would anyone need that? The two most common reasons for using a dual-SIM phone are to have two separate phone numbers and more coverage while travelling.

Using the dual-SIM functionality can also help you save money.

Maybe you already have a plan that offers great tariffs on data, but you found another plan that has great rates for phone calls and text messages.

A dual-SIM device lets you mix and match plans so you could keep your existing plan but use another, like our O2 UK eSIM, on the embedded SIM.

How Does Dual-SIM with eSIM Work?

As mentioned above, a dual-SIM device has two SIM cards. This could be two nano-SIM cards or one nano-SIM and an eSIM. Newer phones use the nano/eSIM combination.

Set up may vary from device to device but it is generally quite a simple process.

With the nano/eSIM combo, you would only have to load the nano-SIM into the tray since the eSIM is already embedded into the phone. To set up the eSIM, you buy an eSIM online and scan the QR code or get one from a mobile carrier and do a manual set up.

Whichever method you use the result is the same – you now have two SIMs each with a separate phone number and network connection. This means you can connect to the internet, make or receive calls, or send and receive messages on both.

However, while the concept is the same, not all dual-SIM devices are created equal. Depending on what dual-SIM mode your phone uses, you will either be able to use both SIMs simultaneously or you will have to alternate between them.

Find answers to frequently asked questions about eSIM

SIM next to open SIM card tray

Different Types of Modes

There are 3 dual-SIM modes:

Dual-SIM Standby (DSS) – This mode is only available on older phones. A Dual-SIM Single Standby phone uses two SIM cards but only one can be active at a time. This mode requires you to specify which SIM can make and receive phone calls.

Dual-SIM Active (DSA) – A Dual-SIM Active phone can use both SIMs at the same time. Both lines are permanently active so if you are on a call on one line and get a call on the other, you will get a notification and be able to switch to the other call.

Dual SIM Dual Standby (DSDS) – Most dual-SIM phones on the market use this mode. DSDS is a hybrid between Dual-SIM Dual-Active and Dual-SIM Single Standby. This means both SIMs are active (i.e. on standby) until you start using one of them.

Benefits of Using Dual-SIM with eSIM

Dual-SIM phones tend to be popular with corporate types and travellers, but they offer many perks that anyone can benefit from. Here are our 5 favourite things about them:

1. Two Numbers, One Phone

The biggest advantage of the eSIM dual-SIM functionality is having two phone numbers.

This is particularly useful if you want to keep your work and personal line on one device and not have to carry around two phones.

2. Freedom to Choose Your Network

Dual SIM phones aren’t locked to a specific network, so you have the freedom to sign up to any mobile network you prefer.

This also means you’re free to use a global eSIM or local SIM when you travel abroad.

3. Mix and Match Phone Plans

A major drawcard of using a dual-SIM phone is being able to use different phone plans.

You could have a voice plan with great rates on one SIM and a plan with excellent data and roaming charges on the other.

4. Cheaper Roaming Tariffs

If you travel often to the UK and don’t want to pay hefty roaming charges, you can buy an eSIM from eSIM.net for your ‘second slot’.

5. More Network Coverage

Being able to use two different plans also means greater network coverage.

If your existing provider doesn’t offer good coverage where you live or work, you can get a plan from a provider that does and increase your network coverage.

two phones on top of each other

Can Dual-SIM Phones Use Different Networks?

Yes. However, phones that are bought on a contract may be locked to the network provider you have the contract with. In this case, you will need to ask them to unlock the phone. Phones bought directly from manufacturers are usually not locked.

Using eSIM services, gives you access to all the major networks, at home and abroad. You could choose to have your primary SIM with a home network and buy a prepaid eSIM plan for the second SIM when you travel.

Bottom line: If your phone is unlocked you can use two different mobile plans.

How Do I Set up Dual-SIM with eSIM?

There are different ways you can get dual SIM functionality depending on what phone you have and which SIM combo you are using (e.g. nano-SIM and eSIM).

iPhones use an eSIM and nano-SIM combination while Android phones may use the nano-SIM/eSIM combination or two nano-SIM cards.


Add an eSIM Service on iPhone

  • Buy an eSIM online
  • Retrieve QR code from email inbox
  • Open the Camera app and scan your QR code
  • Tap the Cellular Plan Detected notification when it appears
  • Tap Continue at the bottom of the screen
  • Select Add Cellular Plan
  • Follow on-screen prompts

The other ways to set up dual-SIM functionality on an iPhone include through a carrier’s app, manually entering the information, or installing a cellular plan.

man setting up dual-SIM phone


Add an eSIM as a second SIM

  • Go into your phone’s settings
  • Tap Network & Internet
  • Select Add next to Mobile Network
  • Tap “Download a SIM instead?”
  • Select Yes when asked, “Use 2 SIMs?” and let your phone update
  • Go to Settings again after your phone updates
  • Tap on Network & Internet and then Mobile Network
  • Go into your networks to set call and text preferences

Add a SIM card as a second SIM

  • Insert the SIM card
  • Select Yes when asked, “Use 2 SIMs?” and let your phone update
  • Go to Settings again after your phone updates
  • Tap on Network & Internet and then Mobile Network
  • Go into your networks to set call and text preferences

The process for setting up dual-SIM on Android phones is quite similar whether you have a Samsung, Motorola, or OnePlus device. We used a Google Pixel 4 for this guide.

Watch a video tutorial for the OnePlus 3T.

Got questions about the eSIM dual-SIM functionality? Search our Helpdesk for lots of useful tips.