Bad service

Bad experience with DMC. I had a debt of 2042,53 with Truworths account was later handed to DMC for collection. Made an agreement with them 02/2024 for at installment of 512 over 4 months. They went on to debit the fifth and sixth installment. Lodged an enquiry with them on the 16 July 2024 and was told my issue will be resolved between 7-14 days. A month later today 15 August 2024 when I contacted them to make follow up of the resolution I was told no one investigated my case and I must WhatsApp them next week.