MTN contract dispute, where account had been paid up since Aug 2021.

I have been struggling to resolve a contract issue I have with MTN since Sep2021. They have listed me again on Experian like last year at the end of March and they try to deduct premiums that I supposedly owe but I have been communicating that I have paid up this contract in Aug of 2021 already with myself and the consultant at the time having agreed on the same but it's as if my credit profile is being sabotaged every year, last year they fixed it in June and it took about 4 months for my score to recover, please help here.