Incorrect billing

I reported more than 3 weeks ago on this site about my billing account that is incorrect and that I am billed at a much higher rate with additional facilities contrary to the contract. I have queried this for some months now without success. On 9/9 Tshepo from Head Office phoned and promised to investigate and lodged yet another query with ref number 843569. Since that day nobody has phoned me again - I receive no correspondence and Tshep does not answer his phone at *** or on the return SMS that I send.