Nightmare Experience with DMC - Paid Settlement Ignored!

I have had the most terrible experience with DMC. They have me under a settlement agreement which was for a 20% discount after owing one of their clients, Markhams. I paid around R4,700 to settle the account. When I called them, they told me to wait for 14 days, which I did. After 14 days, nothing happened. I called them back and sent them proof that I had paid them through their platform, which uses PayFast. They sent me an SMS telling me to wait 7 days as they are processing the payment. They also asked me to send proof of payment, which I did. But still no proof of settlement. Their customer service people have no clue what they are doing, and senior management is nowhere to be found.