Terrible Service

I took up a data deal from MTN via Mondo. An agent made me take up a contract and then I had to pay more than what I had agreed on. I laid a complaint and there was an investigation which found that the agent was wrong. I requested the cancellation of the contract two months after I have received the router but the contract was only closed two months after the request. There is still amount I am owing MTN and Mondo agreed that it was not my fault the balance will credited and that has not happened since June. Every time I call Mondo, I am told they have already sent request to credit my account and the will will escalate to MTN. Now MTN has decided to hand over the contract to the lawyers and that is affecting my credit score.