Worst customer service

I don’t understand why my installment keeps going up, and payment is not allocated proper, as payment is being done by Debt Buster, even sending proof of payment, still payment is not allocated correctly, last I wanted to settle my MR P account but due to funds not allocated I could not settle the amount, now on the 07/01/2025 when I check my balance the December payment did not reflect now the balance is went up by R127,73 from the balance I requested earlier this month. Please sort this urgently