When you’re choosing a SIM-only service, you should try and find out as much as you can about the different tariff rates on offer. Work out how many minutes you spend on the phone each month, how many texts you send and receive, and whether you use additional services, such as internet access, social networking sites or downloading music.
Some SIM-only deals offer free calls to people who are on the same network, so if you make a lot of calls to people who share a network, it may be worth choosing this one.
If you decide to change mobile phone service providers, you should also check that there will be adequate network coverage in your area. Most service providers have an online search tool which allows you to check coverage in your area.