If you're 16-24 in the UK (although I dunno if they check your age tbh) you can get a free pay as you go simcard that gives you 217 texts and 43 minutes free per month, no need to do anything at all, no need to top-up unless you want to, no charges no nothing. They send you advertising MMS messages to subsidise it, but it's not a bad deal really.
www.blyk.co.uk
www.blyk.co.uk