I had the same problem with them over an O2 contract, where I ordered a phone and it just didn't arrive, and when I contacted them they blamed O2 and said O2 were changing their platform or something, for upgrades, so it could take a while to process (days, weeks, months - they couldn't say'). BUT ... I then phoned back and spoke to the cancellation department rather than services and he sorted it for me instantly and the phone arrives tomorrow. He just set up me up for a new contract rather than an upgrade, same cost and I can keep my number - so try that if you are having problems.