Cancelation delay

I had a contract with Telkom since October 2023 and I settled the contract in full May 2024, after settlement I asked them to cancel and close everything for me, come August 2024 I'm receiving smses saying my account is in arrears I should make payment,i called them to find out what's going on because I no longer owe them, they told me that I owe the insurance and I told the lady that I paid everything in May and asked the consultant to close everything for me and they didn't, mid September I saw a debit order from Telkom and I reversed it, I called again the Telkom Insurance and they said my account is active and upto date, and I asked why I'm I getting message while I canceled and they said it's not canceled. I asked again to cancel it this month of October after getting another message from them, and the guy who was helping me said it's a technical error that they're experiencing at Telkom most customers are complaining. So I asked to cancel it again and I got an sms for cancelation but they already affected my credit score.