Unable to cancel contract as requested

2yr contract with Telkommobile expired and I requested to cancel on 15/9 by filling in form in store and signing. They tried once to call to confirm cancellation. I had to go into store again 3 weeks later to get someone to phone me to cancel. They phoned and I confirmed request to cancel. They then cancelled wrong sim nr. Have now phoned and emailed more than 6 times to cancel again and also to rectify bill of over R750 which no one can tell me what it is for. Ansley from The Bridge not able to efficiently help me. He got a general manager to phone me..Nicholas and promised it will be sorted out. Still nothing.