For most people in 2026, a SIM-only deal is cheaper than a bundled pay-monthly contract — often by £200 to £400 over two years. If you already own a phone you are happy with, a low-cost SIM is almost always the winner. Pay-monthly only makes sense if you genuinely want a brand-new flagship and would otherwise struggle to find the cash up front — and even then, only on a fairly priced, ideally 0% deal.
Related reads: best SIM-only deals and mid-contract price rises.
What the two options actually are
A pay-monthly (bundled) contract rolls two things into one bill: the cost of a new handset, spread over 24 or 36 months, plus your airtime (calls, texts and data). You pay nothing or very little up front and walk away with a shiny new phone.
A SIM-only deal is airtime alone. You bring your own phone — the one already in your pocket, a handset bought outright, or one on separate finance — and slot in a SIM. Because you are not repaying a handset, the monthly cost is far lower, and most SIM-only plans are now rolling monthly or 12-month, so you stay flexible.
Why bundled contracts quietly cost more
Three things inflate the price of a bundled deal. First, interest: unless the deal is explicitly 0%, the handset portion often carries an APR, so you repay more than the phone’s cash price. Second, and the biggest trap, is that many contracts keep charging the same amount after the phone is “paid off.” On a 24-month deal, the handset is fully repaid at month 24 — but if you roll on without switching, you keep paying the full bundled price for airtime that a SIM-only deal would give you for a fraction of the cost.
Third, the airtime baked into a flagship contract is usually generous and pricey — large data allowances you may never use. The long-standing rule applies: if you do not get near your allowance, you are simply overpaying.
The worked example: a flagship over 24 months
Let’s price a typical flagship three ways over two years. Figures are illustrative 2026 ballpark prices — always check live deals before you buy — but they reflect what UK retailers and networks are charging.
| Route | Up front | Monthly | 2-year cost |
|---|---|---|---|
| Bundled contract (flagship + unlimited airtime) | £0 | £45 | £1,080 |
| Buy flagship outright + mid-range SIM-only | £999 | £15 | £1,359* |
| Keep your current phone + budget SIM-only | £0 | £10 | £240 |
Reading the maths carefully matters. The bundled contract totals around £45 × 24 = £1,080, and that is before any mid-contract price rises. The buy-outright route is £999 for the phone plus £15 × 24 = £360 of airtime, so £1,359 over two years — but you own the handset outright and can drop to a cheaper SIM whenever you like, or sell the phone later. The keep-your-phone route is the clear winner at roughly £240 over two years.
The headline: if you do not need a new phone, keeping your current one and pairing it with a budget SIM can save you well over £800 across two years versus a flagship contract. Even if you do want that flagship, buying it outright and adding a cheap SIM means that from month 25 onwards you pay just the SIM price — whereas the bundled customer who does nothing keeps paying £45+ indefinitely.
0% handset finance changes the sums
Some networks and retailers now split the handset and airtime into two separate agreements, with the phone on 0% interest finance (for example over 24 or 36 months) and the airtime on a flexible SIM-only-style plan. This is a genuinely better structure than an old-fashioned bundle, because once the 0% finance ends, your bill drops to just the airtime — the “paying after it’s paid off” trap disappears.
The catch: 0% means you pay the handset’s cash price spread out, not a discount. Check that the total of the monthly handset payments matches the SIM-free price, and that the airtime element is competitive on its own. If it is, splitting handset and SIM can give you the cash-flow benefit of a contract without the long-term overpayment.
Side-by-side: which suits whom
| SIM-only | Pay-monthly contract | |
|---|---|---|
| Up-front cost | None (you supply the phone) | Usually £0–£99 |
| Typical monthly cost | £6–£20 | £30–£60+ for a flagship |
| Total over 24 months | Lower — airtime only | Higher — airtime plus handset (plus any interest) |
| Flexibility | High — rolling or 12-month, easy to switch | Low — locked in for 24–36 months |
| Mid-contract rises | Smaller bill, smaller cash rise | Larger bill, larger cash rise |
| Best for | Anyone happy with their phone or buying outright | People who want a new flagship and prefer to spread the cost |
When pay-monthly genuinely makes sense
Bundled or split-finance contracts are not always the wrong choice. They make sense if you want a new flagship now, cannot or would rather not pay £800–£1,200 in one go, and a 0% deal means you pay no more than the cash price. They can also bundle perks — insurance, trade-in credit or streaming subscriptions — that have real value if you would pay for them anyway. The key discipline is to treat the contract as finance: know the total cost, and set a reminder for the month it ends so you can switch to SIM-only rather than drift.
Upgrade culture is the real money drain
The single biggest cost in mobile spending is not the contract type — it is how often you replace the phone. Upgrading every two years on a fresh flagship contract locks you into £1,000-plus cycles indefinitely. Modern phones comfortably last four to five years with a battery replacement, so stretching from a two-year to a four-year replacement cycle roughly halves your handset cost. Pairing an older, still-capable phone with a cheap SIM is the lowest-cost way to own a smartphone in 2026.
Mid-contract price rises hit bundled deals harder
Since Ofcom’s rule change took effect in January 2025, providers can no longer apply inflation-linked percentage rises to new contracts; any increase must be stated up front in pounds and pence. In April 2026, several providers applied fixed monthly rises in the region of £3 to £4 on affected plans. A flat cash rise stings the same in absolute terms on any plan — but on a high £45 bundled bill it is far easier to swallow unnoticed, and you are locked in for the full term. On a £10 SIM-only deal you can simply switch away. Older legacy contracts may still carry CPI-linked rises (for example CPI plus 3.9%), another reason to move onto a modern, transparent deal.
How to switch and keep your number
Moving to SIM-only is quick. Text PAC to 65075 to get your porting code, choose a SIM-only deal, and give the new network your PAC — your number transfers within one working day. Check your current contract has actually ended (or factor in any early-exit cost), make sure your phone is unlocked, and compare deals on a comparison site rather than auto-renewing. MVNOs such as Smarty, iD Mobile, Voxi and Lebara use the same masts as the big networks but often cost 30–50% less.
Frequently asked questions
Is SIM-only always cheaper than pay-monthly?
For airtime alone, yes — SIM-only is almost always cheaper because you are not repaying a handset. The only time a bundle competes is if you genuinely need a new phone and the deal is a fair, ideally 0% one. If you already own a phone, SIM-only wins comfortably.
What happens at the end of a pay-monthly contract?
The handset is fully paid off, but unless you switch, many networks keep charging the same monthly price. That means you carry on paying flagship-contract money for airtime alone. Switch to SIM-only the moment your term ends to stop overpaying.
Can I get a new flagship phone without a bundled contract?
Yes. Buy the handset outright, put it on separate 0% finance, or trade in an old phone, then add a low-cost SIM-only deal. You get the same phone, keep full flexibility, and avoid paying for airtime you do not need.
Do mid-contract price rises affect SIM-only deals?
They can, but the impact is smaller. Any rise on a new contract must now be shown in pounds and pence up front. A fixed cash rise is a much bigger share of a low SIM-only bill in percentage terms, but the absolute amount is the same — and you can switch away easily, unlike on a locked bundled contract.
How much can I realistically save by switching?
Moving from an ended handset contract to SIM-only commonly saves around £25–£30 a month, or roughly £300 a year, according to comparison sites. Keeping your current phone instead of upgrading magnifies the saving further.
Last reviewed: June 2026. This article is general information, not personal financial advice. Prices are illustrative and change frequently — always check live deals and your own contract terms before switching.