Cancellation Impossible

I phoned to cancel my contract and was told the device would be collected the end of the month. It is 2 months later and the device has still not been collected despite numerous follow-ups. Furthermore, they had a debit order go off last month, knowing the service was cancelled and I'd already paid for the month before, meaning I owed nothing. They are extremely quick to sign on but the worst cancellation service I've ever experienced.