MTN BAD ACCOUNTING AND SERVICE

My problems with MTN started in Sept 2020 (I have been a customer for over 20 years) when I upgraded my accounts. I was overcharged the first month of the upgrade i.e charged a pro rata share of the new account but as I had already paid for the month before I should have been credited with a pro rata share of the old account. I have lodged 9 complaints and each time the response is an SMS stating "your Query No..... has been closed. For more information please contact call centre" To date nothing has been done to rectify this. I also have been changed to a new package which I did not ask for at double the rate of my original upgrade and that query has also not been resolved. I cannot get to talk to the accounts dept and for the new package they have tried to put me through to the retentions dept twice. The first time I hung on the phone for 48 mins and the 2nd time 35 mins and nobody answered. I am disgusted at the service of MTN and how their accounts dept have no idea of how to administer accounts. I have been overcharged over R500 rand so far and as a pensioner cannot afford this. I have never had this problem when upgrading before 2020.