Very bad cancellation experience

In June 2024, I took a contract with Mtn and canceled it within 7 days and returned the device to the MTN customer service centre in Constantia. Despite many correspondences to try cancel and stop debit order I have not been helped. It is frustrating and really exhausting. It was my first time dealing with Mtn and I regret even trying them out. *** I need help resolving this matter.