Nu Debt bad service and can't account for the money paid to them even with the provided proof

This company has been calling me to settle my Telkom debt, I settled my debt in May 2024., to date i have been asking for a settlement letter and they have not been responding to my emails nor calls, In August another attorney firm got involved and I was informed that nu debt cannot trace my payment, how is that even possible, I sent them my bank statement and proof of payment yet they say they can't trace my payment, bad service i got from this company after struggling for months and months to get hold of them.. Never make payment to nu debt,