A SIM-only deal is almost always better value than staying on a phone contract once the handset is paid for. For millions of UK mobile users, switching to SIM-only at contract end is one of the simplest and most consistent money-saving actions available. Here is exactly how the maths works and what to do.
The Core Maths
A 24-month phone contract bundles two things in one monthly payment:
- The handset: The cost of the phone, financed over 24 months
- The airtime: Calls, texts, and data
When the 24 months end, the handset is paid off — but most networks keep charging the same amount. You effectively pay for a phone you already own.
Example:
- Phone contract: £42/month × 24 months = £1,008 total
- After 24 months, staying on contract: £42/month = £504/year just for airtime
- Equivalent SIM-only deal: £12/month = £144/year
- Annual overpayment by staying on contract: £360
Over two more years of inaction: £720 wasted.
Worked Comparison — Monthly Contract vs SIM-Only
| Option | Monthly cost | Includes | Annual cost |
|---|---|---|---|
| Phone contract (24 months) | £42 | Handset + SIM | £504 |
| Same contract, month 25+ | £42 | SIM only (handset paid off) | £504 |
| SIM-only equivalent deal | £12 | SIM only (same data) | £144 |
| Saving by switching | £30/month | £360/year |
How to Switch to SIM-Only
Step 1 — Check your contract end date
Log in to your provider’s account or check your contract documents. Most phone contracts are 24 months. Switching before this incurs early termination fees.
Step 2 — Request a PAC code
Text “PAC” to 65075 (free, from any network). You’ll receive your PAC code by text within 1 working day. Do this before signing up with a new provider.
Alternatively, ask your provider in a live chat or phone call.
Step 3 — Compare SIM-only deals
Compare by:
- Data allowance (how many GB do you actually use? Check your phone’s settings)
- Contract length (monthly rolling = maximum flexibility; 12-month fixed = slightly lower price)
- Network coverage (check the Ofcom coverage checker for your area)
- 5G vs 4G (5G gives faster speeds where available)
Step 4 — Sign up with your new provider and give them your PAC
Your new provider handles the rest. Your number transfers automatically — typically within 1 working day.
Step 5 — Swap your SIM
Insert the new SIM or follow eSIM setup instructions (available on iPhone 14+ and newer Android flagships).
How Much Data Do You Need?
Check your current phone’s data usage: Settings → Mobile Data (iPhone) or Settings → Network (Android).
| Monthly data | Typical user | SIM-only cost range |
|---|---|---|
| 1–5GB | Light: browsing, maps, messaging | £5–£10/month |
| 5–20GB | Moderate: social media, some streaming | £8–£15/month |
| 20–50GB | Heavy: video streaming on mobile, hotspot | £12–£20/month |
| Unlimited | Very heavy: constantly streaming, hotspot | £15–£25/month |
What About 5G?
5G SIM-only plans are now widely available at little or no premium over 4G. If you have a 5G-compatible handset and 5G is available in your area, choosing a 5G SIM-only plan costs approximately the same as 4G but delivers faster speeds where the network is available.
When a New Phone Contract IS Worth It
SIM-only is not always the right answer. A phone contract can make sense if:
- You need a new phone now and cannot afford to buy one outright. A contract spreads the cost of a new handset over 24 months — essentially an interest-free loan if you choose a contract over a separate credit agreement.
- Your current phone is outdated or broken. Using an unusable phone on a SIM-only deal is not a saving.
- You want a specific device at launch. New flagship phones (iPhone 16, Samsung Galaxy S25) are often only available on contract at launch before stock hits the secondhand market.
In these cases, compare the total contract cost (monthly × 24) against the price of buying the phone outright + SIM-only cost over the same period. Contracts are often priced at or near the retail cost of the device — meaning no significant premium for spreading payments — but some operators charge more than the phone’s standalone retail price when you factor in the airtime cost.
Refurbished Phones — A Third Option
If you want to upgrade your phone without committing to a 24-month contract, a certified refurbished device is worth considering:
- Back Market, Refurb’d, and Envirofone sell certified-refurbished phones at 20–40% below new retail price
- Apple’s own certified refurbished store sells iPhones with a 1-year warranty
- Grade A refurbished means no visible damage and full functionality — effectively equivalent to new
Example: A new iPhone 15 costs approximately £799. A Grade A refurbished iPhone 15 from Back Market costs approximately £550–£600 — saving £200–£250 outright. Combine with a £12/month SIM-only deal versus a £45/month contract and you save significantly over two years.
eSIM and Dual SIM
Modern phones increasingly support eSIM — an embedded digital SIM alongside a physical SIM slot. This means you can:
- Use two numbers on one phone (e.g., personal and work)
- Switch networks instantly by activating an eSIM deal without waiting for a physical card
- Keep a roaming eSIM active for travel without swapping your main SIM
iPhones from the iPhone 14 onwards support eSIM-only (no physical SIM slot in US models, physical SIM retained in UK models). Android flagships from Samsung, Google Pixel, and OnePlus support dual-SIM via eSIM + physical SIM.
Check whether your phone is eSIM compatible before choosing a provider that requires it.
For more on reducing your phone bill, see How to Cut Your Phone Bill UK.