POOR SERVICE AND BILLING ISSUE RESULTING IN DEACTIVATION

I am writing this on behalf of my father. He paid for the Month of December 2020, they deactivated his account saying he was in arrears and asking that he must forward POP. He went into MTN Store, Table Bay mall - Blouberg and dealt with Mishelle Visser, gave her his Bank Statement. they activated the account, Now they have deactivated the account again claiming he is in arrears for the exact same month. He has gone in again to take POP and STILL nothing has happened. somewhere someone is not doing their Job, I need resolution for this ASAP!!