Acoount paid up but MTN refuses to close account

Good Day. My mom had her MTN account handed to the lawyers for collection and she has been making payments. We have received a statement from Saya Recoveries that the account is paid up and that MTN should cancel or close the account. She then went to MTN Goldfields Mall in Welkom but wa advised that there is still two thousand rands outstanding. Meaning that the information with Saya Recoveries does not correspond with the one that MTN has. This is frustrating for my mom.