vodacom contract

I happen to have had a contract with vodacom for so many years until 214 when they contacted me to upgrade my contract and I requested to terminate /cancel my contract. They informed me I would have to do that telephonically which I did in November 2014. Then mid 2015 I get contacted by a certain VVM debt collectors who inform me my vodacom account has been handed in to them as I am owing on the account. I inform the debt collectors that I terminated that contract therefore I do not understand what they are talking about. They inform me to clear the issue with Vodacom, When I get to vodacom I am informed that they are not able to see anything in my account/on the number since the number is deactivated. They give me a certain print out to send to VVM in showing VVM that the account is deactivated. 1. I do not understand why I should be the one giving VVM my information since they handed me over. Then VVM informs me the information is not sufficient and I should go back to vodacom and clear the issue since they handed me over. The back and forth went on for over six months until now Jan 2016 VVM ppl dont stop calling me daily. I decide again to call vodacom and query the issue