Paid up account

My name is David Mpitso I had a contract with CELL C which was handed to SSDA and I made a FULL PAYMENT of R1568.59 on 02/11/2021 and they acknowledged and closed the account via email, since then they giving me the runaround for paid up letter & the amount still appears on my credit profile they don't want to clear my name, I'm still in AREAs with that account please help because everywhere I apply for credit I'm told to pay CELL C first PLEASE HELP