Contract billing

I have a contract with MTN that I signed an agreement with them for the amount of R750 however every month they bill me more than the agreed amount when I call the customer service all the agents I spoke to were telling me a different story.

I requested a recording of the call between me and agent still they failed to provide one. I request for my invoice still they failed to send it to me.

The service is extremely horrible team leader couldn’t assist me as well