Idiots in the billing dep[artment

I have a billing issue which both the manager of customer service and the manager of the billing department seem to think I am a fool. If you wrongly bill me R1704. should you not credit the account with the same amount you wrongly billed me? I have been calling them since July 2021. and the more I try and should them the error I get ****ed off. I get told they will call me back it only happens when I call the following day. I have wasted time trying to get this matter sorted but it seems that it only falls on deaf ears. This is really not how I thought that it would be when I signed up.