Mtn accounts dept very bad

I've been having a problem with mtn accounts dept for overcharge not credited on 2 accounts. One is pending for over 2 years on cell numbers ********** 787 and ********** 949 where i was overcharged on inception. The store manager at overport branch told me he 'll follow up on it but nothing happened and I complained once again to new manager. He promised he 'll sort out the overcharge but he hasn't done so to date. The second account overcharge is from June 2018 when I did a renewal. I was overcharged for 4 months but all i get is ref numbers from customer care for query but no credit. I also brought this to the attention of store manager and staff at overport branch. I am now being correctly charged but what about the credit for the overcharge?? Cell number in question here is ********** 009. Very frustrated. Nasreen Moosa ********** 009