MTN query

I have been trying to solve an incorrect billing issue with MTN for over a year. Last year May, they started billing me for content on my monthly contract invoice. I never signed up for content. I had to investigate this matter with no help from MTN. The content billing was ex WASPA. I eventually got an email from WASPA confirming that I never signed up for content. This mail was sent to MTN last year and I am still waiting for my credit for just under R600.00. I keep on being advised that my query has been escalated. This is unacceptable. MTN billed these amounts supposedly on behalf of WASPA. This money is due to me.