Multi-fit SIM Card (nano, micro and standard) so they are guaranteed to fit all phones. The SIM Card self activates when you insert it into your phone and most come loaded with high speed data, unlimited minutes and unlimited texts. Prepaid mobile plans in the UK are a great way to keep your mobile data costs under control. You won’t get any nasty surprises and you’re not tied into a long-term contract that stops you switching to a better deal when it comes along.