Bad customer service

I took a 36 months cellphone insurance with telkom i called to customer service line in Dec i was told to cater for end of Jan as my last instalment to cancel to contract. End of Feb they tried debiting my account n they were no funds around April a friend told me she's receiving my messages from telkom that i owe them i tried calling n requesting recording no help and now they have listed me on bureau as a bad payer