If your phone contract has ended and your handset is still working perfectly, switching to a SIM only deal is one of the smartest ways to cut your mobile costs. With an O2 SIM only plan, you get the same network, coverage, and perks but without paying for a phone you already own. Many customers save hundreds of pounds over the course of a year by making this simple switch.
This guide compares the current O2 SIM only plans, explains what is included, and helps you decide whether a SIM only deal is right for your situation.
What Is a SIM Only Deal?
A SIM only deal provides you with a mobile plan (calls, texts, and data) without including a handset. O2 sends you a SIM card (or eSIM) which you insert into your existing phone. Because you are not paying off the cost of a device, SIM only plans are significantly cheaper than phone contracts.
SIM only is ideal if you already own a phone you are happy with, whether it is a device you have paid off through a previous contract, a phone you bought outright, or a second-hand device. You get the same O2 network experience at a fraction of the price.
Current O2 SIM Only Plans
O2 offers a range of SIM only plans to suit different usage levels. Here is an overview of the typical tiers available:
| Data | Minutes | Texts | Contract Length | Typical Monthly Cost |
|---|---|---|---|---|
| 1GB | Unlimited | Unlimited | 12 or 24 months | From around £6/month |
| 10GB | Unlimited | Unlimited | 12 or 24 months | From around £10/month |
| 30GB | Unlimited | Unlimited | 12 or 24 months | From around £14/month |
| 100GB | Unlimited | Unlimited | 12 or 24 months | From around £18/month |
| Unlimited | Unlimited | Unlimited | 12 or 24 months | From around £25/month |
SIM Only vs Phone Contract: Cost Comparison
The savings from switching to SIM only can be substantial. Here is a typical comparison over 24 months:
| Plan Type | Monthly Cost | 24-Month Total | What You Get |
|---|---|---|---|
| Phone Contract (30GB + device) | Around £45/month | Around £1,080 | Phone + 30GB data |
| SIM Only (30GB) | Around £14/month | Around £336 | 30GB data (use existing phone) |
| Savings | £31/month | £744 over 24 months |
Even if you factor in buying a phone outright (which often costs less than the total device payments in a contract), SIM only usually works out cheaper overall. For more savings ideas, check our guide to reducing your O2 bill.
Contract Lengths: 30-Day vs 12-Month vs 24-Month
30-Day Rolling Plans
Maximum flexibility. You can cancel or change your plan every month with just 30 days notice. Ideal if you are between contracts, testing O2's network, or want the freedom to switch at any time. Monthly costs are slightly higher than longer commitments.
12-Month Plans
A good middle ground between flexibility and value. You commit for a year and get better pricing than 30-day plans. After the 12 months, you can switch, upgrade, or roll onto a monthly basis.
24-Month Plans
Best value per month but the longest commitment. Suitable if you are confident you want to stay with O2 and your chosen plan for two years. Offers the lowest monthly costs.
What Is Included with O2 SIM Only Plans?
O2 SIM only plans come with several benefits beyond just calls, texts, and data:
- O2 Priority: Access to exclusive offers, early access to event tickets, and weekly freebies through the O2 Priority app
- O2 WiFi: Free access to O2's network of WiFi hotspots across the UK
- Data Rollover: Unused data carries over to the next month (on eligible plans)
- EU Roaming: Use your UK allowance in Europe at no extra cost (subject to fair use limits)
- WiFi Calling: Make calls over WiFi when mobile signal is poor
- 5G at No Extra Cost: Access to O2's 5G network where available, included in the plan price
- Flexible upgrades: Check your upgrade eligibility when you want to move to a phone contract
O2 SIM Only for Existing vs New Customers
Existing O2 Customers
If your current O2 contract has ended and you want to switch to SIM only, you can do so easily through the My O2 app, by calling O2, or by visiting a store. Your phone number stays the same and there is no disruption to your service. O2 may also offer you exclusive retention deals if you contact them about switching.
New Customers Joining O2
If you are joining O2 from another network, you can keep your existing phone number by requesting a PAC code from your current provider. O2 will port your number across, typically within one working day. You can order your O2 SIM only plan online at o2.co.uk, in-store, or by phone.
O2 SIM Only vs Competitors
| Feature | O2 | EE | Three | Vodafone |
|---|---|---|---|---|
| Cheapest SIM Only | From £6/month | From £8/month | From £5/month | From £8/month |
| Unlimited Data | From £25/month | From £28/month | From £18/month | From £26/month |
| Data Rollover | Yes | Selected plans | No | Selected plans |
| EU Roaming | Included | Included | Included | Included |
| 5G Included | Yes | Yes (on 5G plans) | Yes | Yes |
| Perks/Rewards | O2 Priority | EE Perks | Three+ Rewards | VeryMe Rewards |
| 30-Day Plans | Yes | Yes | Yes | Yes |
For a more detailed network comparison, see our O2 vs EE comparison guide.
Tips for Choosing the Right Data Allowance
- Check your current usage: Before choosing a plan, look at your recent bills to see how much data you actually use each month. Most people overestimate their needs
- Light users (under 5GB): If you mainly use WiFi and only use mobile data for emails, social media browsing, and maps, a 1-3GB plan should suffice
- Moderate users (5-20GB): If you stream some music, use social media regularly, and occasionally watch short videos, 10-30GB is typically enough
- Heavy users (20GB+): If you stream video regularly, use your phone as a hotspot, or rarely connect to WiFi, consider 100GB or unlimited
- Remember data rollover: With O2's data rollover, any unused data carries to the next month, giving you extra buffer during heavy-usage periods
Frequently Asked Questions
Can I keep my phone number when switching to O2 SIM only?
Yes. If you are switching from another network, request a PAC code from your current provider and give it to O2. Your number will be ported across. If you are already on O2, your number stays the same automatically.
Can I use any phone with an O2 SIM only deal?
Yes, as long as your phone is unlocked or locked to O2. If your phone is locked to another network, you will need to get it unlocked first. Most phones purchased since 2022 are sold unlocked in the UK.
What happens at the end of my SIM only contract?
When your SIM only contract ends, you roll onto a 30-day plan at the same or a slightly adjusted price. You can then continue month-to-month, sign up for a new SIM only deal, or switch to a phone contract.
Can I add a phone later and switch to a full contract?
Yes. If you decide you want a new phone, you can upgrade to an O2 Refresh contract at any time (if you are out of your minimum term). Check your upgrade eligibility through the My O2 app.
Is there a credit check for O2 SIM only?
Yes, O2 runs a credit check for monthly SIM only plans. If you prefer to avoid credit checks, O2 also offers Pay As You Go options which do not require one.
Can I get an eSIM with a SIM only deal?
Yes, O2 offers eSIM as an option for SIM only plans. Instead of receiving a physical SIM card, you download your SIM profile digitally onto your compatible device.
Need Help Choosing the Right SIM Only Plan?
Our independent O2 specialists can analyse your usage, compare plans, and help you find the SIM only deal that saves you the most money. We can also check your upgrade eligibility if you are considering your options.