Bad Service and Incorrect information

I am very displeased and disappointed and disgusted by MTN. I took out a contact last year end of December and l was told by the Agent Rep at there store that I'll only be starting to pay for it end of January and to my surprise they started billing me end of December. So I went back to conceal the contact in due time and notice and also after seeing that the amount of data I was receiving was not the same as the data l should have been provided and their router kept on turning on and off. I went to cancel the contract and they ignored me and told me l could not cancel it anymore.. I'm very upset because now they are affecting my credit score badly on something that is there fault.