My O2 contract was coming to an end. When I called 202 and asked for the PAC to change provider they offered me this deal; Keep my sim card and number, Online 25 tariff, reduced to £10 per month, but free for first 15 months, so total cost for 200 mins/400 txt per month for 18 months is £30. They credit you with £150 at the start, and take £10 each month. Obviously, if you go over the 200/400 and premium calls, that comes off the total, but still a good deal. I was paying £35 a month. I've got the same phone, same sim, less mins but wasn't using them, and now I'm paying £0. Result.