Telkom poor services

I am currently using telkom for my home wifi. All of a sudden they start overcharging me and they cannot explain why. Whenever I make an inquiry I'm being told that they will look into it and this has been happening for 3 months now. I was told I would be credited the severely overcharged amounts. Guess what: not even the billing department can locate the error. What they did was acknowledge that they have been severely overcharging me. I use telkom because it came highly recommended but from my experience it is a practical joke.