They might love music, but Three certainly do not love customer service.
My other half cancelled her three mobile approximately two years ago. A week ago she got a later stating that she owes them some money (a small sum - probably half a months line rental). Upon trying to complain about the fact that it took two years to ask for this cash - she was put on hold for an hour, with no end in sight.
It wasn't until I phoned up and made some noise including the magic words "OFCom" and "Trading standards" (and incidentally getting the agent on the other end to admit that three had probably made silent calls to our landline during their alleged attempts to contact her), that she finally got some answers.