INCORRECTLY BILLED TWICE & NO ASSISTANCE FROM MTN

My business has a contract with MTN for which I am supposed to be billed R539 .01, on 30 June 2023 I was billed R 2 819.01. I called MTN on 10 July, and they resolved that I was incorrectly billed and needed to be credited. I have been calling the entire month of July but have gotten no assistance as the matter has been escalated to the supervisors. I have been promised to receive a call from the supervisors to effect my credit, but I have not received the call. To make things worse, I was again billed the R 2 819.01 on 30 July 2023. The level of poor service is very dis-heartening.