Cancellation is impossible

I simply cannot get through to the cancellations department . I have two reference numbers where I was told someone would get back to me and still no joy. If I don't make payment I will get a call to say I owe them but to cancel no one can help me. The service is poor as I have two contracts for upgrade , I chose to upgrade one and received immediate assistance and the contract was upgraded , on the second which I have been trying to cancel since last year , no one can assist me .