Virgin Mobile offer some great SIM Only deals. There is no long term contract, no need to change your phone number and you can keep your existing phone. Virgin Mobile offer a SIM Only with with 150 minutes and 1000 texts for only 15 pounds per month. As well as this Virgin also offers a 10 pounds SIM Only with 200 minutes and 200 texts! Don't forget this is a 30 day contract so you can cancel at anytime!