Bad Service

I'm an extremely irate ex client of Vodacom. I had a internet access through Vodacom which was terminated as the contract had lapsed but was still paying for the service, the SIM card had been deactivated & couldn't be used. I cancelled with cancellations dept earlier this year & now I get a letter of demand for and outstanding amount of R 320 for acct no and that I will be listed. I find this unacceptable investigate & advise by end of business tomorrow or I will escalate further. I also want in writing confirmation from Vodacom that I have not been listed I can't get any assistance from the Vodacom shop nor the call center and all I get is the run around Sue Brown