Transfer Your Phone Number to an eSIM in the UK
You won't lose your phone number when switching to an eSIM — you keep it by using a PAC code or an in-app transfer, depending on your situation. This guide is for anyone in the UK who wants to move to an eSIM without starting fresh on a new number.
There are three main paths depending on where you're starting from: switching your existing number to an eSIM on the same network, porting your number from one network to a different eSIM provider, or adding an eSIM like Fuse Mobile alongside your current SIM. Each path is straightforward once you know the steps.
Why You Won't Lose Your Number
Your phone number is tied to your account, not your physical SIM card. Whether you're moving from a plastic nano-SIM to an eSIM, or switching networks entirely, the number travels with you.
The mechanism that makes this possible is called number portability — a legal requirement for all UK mobile networks. Ofcom mandates that any UK provider must release your number to you on request, usually within one working day. You're entitled to it. No provider can hold it hostage.
The two tools you'll use are:
- PAC code (Porting Authorisation Code) — used when switching to a different network
- In-app or online eSIM transfer — used when staying on the same network
Path 1: Same-Network eSIM Switch (Keep Your Number, Change Your SIM)
If you're happy with your current network but want to upgrade from a physical SIM to an eSIM — perhaps because you've bought a new phone — this is the simplest route.
Step 1: Check eSIM eligibility
Confirm that your current network supports eSIM and that your handset is eSIM-compatible. Most iPhones from the XS onwards and Android flagships from 2020 onwards support eSIM. Check your phone's settings:
- iPhone: Go to Settings → General → About → scroll to Available SIMs
- Android: Go to Settings → Network & Internet → SIMs → look for an Add eSIM or Download a SIM option
Step 2: Request an eSIM from your provider
Contact your current network — via their app, website, or customer service — and ask to convert your existing SIM to an eSIM. Most major UK networks offer this through their self-service app.
You'll typically be asked to verify your identity and confirm your account details.
Step 3: Receive and scan your QR code
Your provider will send you an eSIM QR code by email or display it in their app. You then:
- Open Settings on your phone
- Navigate to Mobile Data (iPhone) or Network & Internet → SIMs (Android)
- Tap Add eSIM or Add Mobile Plan
- Scan the QR code using your camera
- Follow the on-screen prompts to activate
Step 4: Confirm your number is active
Once activated, your existing number will be live on the eSIM. Your old physical SIM will be deactivated automatically — don't discard it until you've confirmed everything is working.
Tip: Do this over Wi-Fi. You won't have mobile data during the brief switchover window.
Path 2: Port Your Number to a New Network (PAC Code Transfer)
This is the path most people take when switching providers — for example, moving to Fuse Mobile while keeping your existing mobile number.
What is a PAC code?
A PAC (Porting Authorisation Code) is a unique nine-character code that authorises your new provider to claim your number from your old one. It's valid for 30 days from issue.
Step 1: Get your PAC code
You have three ways to request it:
- Text 'PAC' to 65075 — your code arrives by text within 60 seconds, free of charge
- Call your current provider — they must provide it immediately on request
- Use their app or website — most major networks now offer this in their account portal
Your provider is legally required to give you the code immediately. They may ask why you're leaving — you don't have to answer — but they cannot delay or refuse.
Step 2: Sign up with your new provider
Create your account with your new network before submitting the PAC code. For Fuse Mobile, you can start with a 7-day free trial — 500MB of data with no payment details required upfront — and then choose a plan before porting your number across.
Step 3: Submit your PAC code
Provide the PAC code to your new provider during or after sign-up. They'll handle the porting process on your behalf. You'll usually need to supply:
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- Your PAC code
- Your current phone number
- Your account details (name, address, sometimes your account number)
Step 4: Wait for the port to complete
Number ports in the UK typically complete within one working day, often faster. Your new provider will confirm when it's done. During the brief switchover — usually just a few minutes — you may lose signal on both the old and new SIM simultaneously.
Step 5: Activate your eSIM
Once ported, activate your eSIM using the QR code from your new provider. With Fuse Mobile, this is done via the Fuse app or by scanning the QR code sent to your email.
Warning: Don't cancel your old contract before the port completes. If you cancel first, your number may be released and lost. Always port first, cancel after.
Path 3: Add an eSIM Alongside Your Current SIM (Dual SIM)
If your phone supports dual SIM (one physical SIM + one eSIM), you don't have to port your number at all — at least not immediately. You can run both simultaneously.
This is particularly useful if you:
- Want to trial a new network before committing
- Travel frequently and want a data eSIM for roaming without losing your UK number
- Are on a contract you can't exit yet
How it works
Most modern iPhones (XS and later) and many Android devices support Dual SIM Dual Standby (DSDS), meaning both SIMs are active at the same time. You can assign each SIM a role:
- Primary SIM: your existing number, calls and texts
- eSIM: data, or a second number
With Fuse Mobile's eSIM, your phone automatically connects to whichever of the four UK networks — EE, Three, Vodafone, or O2 — has the strongest signal in your location. That makes it a strong choice as a data eSIM even before you decide to port your main number across. Find out more about how Fuse's multi-network eSIM works.
Setting up dual SIM on iPhone
- Go to Settings → Mobile Data
- Tap Add eSIM
- Scan your Fuse QR code
- Label each line (e.g. "Personal", "Fuse Data")
- Set your preferred line for calls, texts, and data under Default Line
Setting up dual SIM on Android
- Go to Settings → Network & Internet → SIMs
- Tap Add eSIM or the + icon
- Follow the prompts to scan your QR code
- Assign roles to each SIM under SIM preferences
Which Path Is Right for You?
| Your situation | Best path |
|---|---|
| Staying on the same network, new phone | Path 1 — same-network eSIM switch |
| Moving to a new network permanently | Path 2 — PAC code port |
| Still in contract, want to trial an eSIM | Path 3 — dual SIM |
| Frequent traveller wanting roaming data | Path 3 — dual SIM with Fuse Pulse or Surge |
Porting to Fuse Mobile: What to Expect
Fuse Mobile is a UK eSIM provider that connects to all four UK networks — EE, Three, Vodafone, and O2 — automatically choosing the strongest signal wherever you are. There are no contracts, and plans roll monthly.
If you're porting your number to Fuse, here's the typical timeline:
- Sign up and activate your Fuse eSIM — you'll get a temporary Fuse number immediately, and data works straight away
- Submit your PAC code in the Fuse app
- Port completes — usually within one working day. Your existing number replaces the temporary one
- Cancel your old contract only after confirming your number is live on Fuse
Fuse's Pulse plan (10GB, £9.99/month) includes roaming in 130+ countries and is the most popular option for people switching from a traditional single-network SIM. If you primarily need UK data, the Spark plan (5GB, £5.99/month) is a straightforward starting point.
Not sure yet? The 7-day free trial gives you 500MB to test Fuse's coverage before you commit to porting your number.
Common Mistakes to Avoid
Cancelling your old contract before porting This is the most common error. If you cancel first, your number enters a release queue and may be permanently lost. Always complete the port before cancelling.
Using an expired PAC code PAC codes are valid for 30 days. If yours expires, simply text 'PAC' to 65075 again to get a fresh one.
Scanning the QR code on the wrong device Your eSIM QR code is tied to one device. Don't scan it on a different phone from the one you intend to use. If you scan it on the wrong device, contact your provider — most can issue a replacement code.
Assuming eSIM means losing your number It doesn't. Your number is account-level, not SIM-level. The transfer process is designed specifically to preserve it.
FAQ
Will I lose my phone number when switching to an eSIM?
No. Your phone number is linked to your account, not your SIM card. Whether you're switching to an eSIM on the same network or porting to a new provider, your number transfers with you via a PAC code or in-app process.
How long does it take to port a number to an eSIM?
In the UK, number ports typically complete within one working day — often within a few hours. During the brief switchover window (usually just minutes), you may temporarily lose signal on both your old and new SIM.
Can I keep my number if I switch to Fuse Mobile?
Yes. You port your number to Fuse using a PAC code, which you can get instantly by texting 'PAC' to 65075. Submit the code in the Fuse app and the port usually completes within one working day. Your existing number then becomes active on your Fuse eSIM.
What if my phone doesn't support eSIM?
eSIM requires hardware support built into your phone. If your device doesn't support it, you'll need a physical SIM instead. Most smartphones released from 2020 onwards support eSIM — check Settings on your device or look up your model's specifications.
Can I run my old SIM and new eSIM at the same time?
Yes, if your phone supports Dual SIM (one physical SIM + one eSIM). This lets you keep your existing number active while trialling a new eSIM provider. iPhones from the XS onwards and many Android flagships support this configuration.
Summary
Transferring your phone number to an eSIM in the UK is a straightforward process — you're protected by Ofcom's number portability rules, and no provider can prevent you from taking your number with you.
The right path depends on your situation: request an eSIM conversion from your current provider if you're staying put, use a PAC code if you're switching networks, or run both SIMs simultaneously if you're not ready to fully commit yet.
If you're considering Fuse Mobile, the 7-day free trial is a low-risk way to test multi-network coverage before porting your number across. When you're ready, explore Fuse's monthly plans — all rolling, no contracts, with roaming included on Pulse and Surge.