Incorrect bill

I have been an MTN customer for many years with 5 contracts. I have never missed a debit order or been late on a payment. My monthly debit order is around R1850. For the month of August 2021 I've been charged R11035. I have queried the amount with MTN and was advised I'll get feedback in 3-5 working days, however to this day I have not been contacted. I reversed the debit order and paid in store the requested amount of R2246, but my lines have still been deactivated. I get an sms to pay R8800 or my credit record will be affected, but not a single consultant at MTN is able to tell me where that amount of R11035 came from. All the consultants can do is an escalation, but once the call is ended nobody calls me back yet it's a month later. I will pay this R8800, but I need MTN to contact me and then credit my account afterward. Pathetic service!!!!!