Unresolved MTN Samsung Trade-in device Promotion no refund

Now, this is the third problem with MTN in two years! This complaint relates to the Samsung trade-in promotion on 23 Nov 2023, when we are still waiting for a full credit of R417,40 per month, not only R16.67! MTN is demanding the outstanding balance from us for the contract, threatening to suspend our lines and give us a bad credit rating. We have been to the MTN Store on numerous occasions and called MTN directly without success for five months without any conclusion. MTN is the culprit, not us! The aggregation is overwhelming!!