Tshwane Municipality making me sick

Can someone please advise me on how to escalate a matter of incorrect billing and constant threats by this Municipality. I get a statement that does not account for the large lump payments I made, but keep getting charged interest on the wrong amounts. This **** also involves supposedly physically sending your billing to a wrong address just so they can charge for that too (when they have my actual address and email).

My emails to their credit division remain unanswered. I once got an sms apologising for the incorrect billing. I made sure to save it in my compiling a file to escalate it.

Is there a regulation authority: Ombudsman? A state director general or someone like that who handles these? Can I take legal action?