Very poor service from MTN and Vodacom

I wanted to cancel my MTN contract and insurance, and with a long story that i will not be able to use my number any more, i down graded the contract without a phone, and canceled the insurance, its been more than 3 months now, MTN is still billing me alot more that what was agreed apon, when you call they tell you its the insurance when you call the insurance they tell you its MTN, and still struggle with the Contract to be corrected, this is not the first time, this also happend with my Vodacom contract.