Check your last few months of data use before choosing a plan. Paying for an allowance you rarely touch can cost more than an occasional upgrade later.
Choose the handset before comparing contracts
Think about what your current phone no longer does well. Battery life, storage or a damaged screen may be the real problem; a newer camera may make little difference to you. Decide which features matter before comparing the monthly payments.
Check the exact model, storage capacity and condition in each offer. If a device is refurbished, read the description and warranty rather than comparing it as though it were a new handset.
Keep handset payments and airtime clear
Add the upfront payment to the scheduled payments over the stated term. Read whether the device and airtime have separate agreements or different end dates. Ask what you would still owe for the phone if you changed the airtime plan.
Compare a phone bought separately with a SIM only deal over the same period. The better choice depends on the prices and payment arrangements available to you, so use the actual totals rather than assuming one route is always cheaper.
Check coverage where you spend time
Look at coverage at home, work and other places you use your phone regularly. Ofcom's coverage map is a useful starting point; compare it with the network's own checker and remember that predictions are not a guarantee inside every building.
Check roaming terms, tethering and any limits attached to the data allowance. If you travel, use the countries you actually visit when checking the conditions. Keep your existing contract and any outstanding device balance in mind before switching.
Questions before you compare
Can I keep my mobile number?
For a single UK mobile number, you can request a PAC by texting PAC to 65075 and give it to the new provider. Check existing charges and the provider's switching instructions first.
Would SIM only be better if my phone still works?
Compare it before buying a new handset. Keeping a phone you are happy with avoids taking on another device purchase just to change your mobile plan.