MTN is robbing me

I had an account with mtn back in recent years.i paid up my account by december 2023 through nu debt management.an they did provide me with paid up letter and i did share it with you guys and shapiro shakes.i went to mtn store by riverside nelspruit wsnted to take a new contract or upgrade since i once be an mtn customer but thet said no i must start from bottom and i got declined.by january i started to recieve a statement which i never understood it.then i went to the branch for clearance and they told me mtn is owing me and it is not possible the mtn number because they already give it to someone else i said owk...by february i recieve another ststement i ignored it..by march i recieve another statement then i went to mtn last week thurthday an i found out that someone at your company re activated simcard or device by december 2024 wuthout my knowledge..i spent more than 1hr30 min on the phone with the mtn customer care but all of them they always transfer my call through department..today they phoned me twice demAnding payement..i ended up went to mtn store and do the payement because you guys you gonna ruin my name....how can you do this kind of things and you call yourselfs professionals