Vodocom is hanging on to my contract

I am trying to cancel my Vodacom contract since last year. I had this contract for many years. However, it seems to be an impossible task. I have send numerous e-mails to Vodacom and even went to one of the service centers. I am not using the device and phone number since the beginning of the year, and was told that i am owing nearly R6 000 on this contract, although i have made no calls in the 4 last more than 6 months. All i want is to just pay what i must pay to close this damn contract. Every time i enquire i am told that my contract expires at different dates. I just want to stop it NOW and get this over and done. As i have said this seems to be an impossible task and it is in no way how you treat a long standing client.