Incorrect billing and MTN store and Call centre not willing to assist.

I upgraded to a new contract at the end of June 2021. The total contract is R759, however, I have been charged +-R1200 on my June and July invoices. The My MTN app is currently saying that my estimated "Bill so far" is also going to be over R1200. My usage limit has been set to 0.00 from the start.

I have tried to get answers through the MTN store as well as the 135 call centre without any success.