Telkom dispute

I'm writing to dispute the outstanding balance on my Telkom account. The account was handed over to Debtin for settlement, and I made arrangements to pay the agreed-upon amount. I received a paid-up letter from Debtin, confirming settlement. However, Telkom claims I still owe R10,000.

Telkom directed me to request a credit from Debtin, but Debtin stated that Telkom didn't provide them with the full account details, specifically regarding a reversal last year. Debtin claims they communicated with Telkom about the discount, so it's unclear why the settlement wasn't processed correctly.

I believe it's unfair to expect me to pay the outstanding balance without the discount, given that I settled with Debtin based on the agreed terms. I have emails and a settlement letter from Debtin as proof. I'd appreciate assistance in resolving this matter.