SIM Cards for the major networks

There are 60 million mobile phones in circulation in the UK and all of these need SIM cards to work. The reasons for people buying SIM cards vary:

To get a better tariff or bundle
Phones are often free to purchase but the tariff included on the SIM will be quite expensive. People often get a free phone, use the free bundles the SIM comes with and then switch to a SIM with a better price-plan.

To Get Special Features
Some SIMS have special features such as; cheap text bundles, cheap calls to landlines or numbers on the same network.

Better network coverage
Mobile phones are often purchased without regard to the SIM's network and coverage. Often people find after buying a phone that the SIM's network is not covered in the region in which they live so, they can purchase a SIM of a different network provider's (usable where they live) from you.

Switching to 'Pay as you go'
Helps the user control expenditure on their phone bill and save money on monthly line rental!