Dishonest and bad customer service

I canceled my contract with Telekom on the 17th December 2025. They said they will Derbit R6000 on January including penalty, I then I asked if Iam paying it now how much will I have to pay they said 4500. I payed and I have been doing a follow up wanting settlement letter. Today 6 January 2026 I received billing email that they will Derbit R3 647. When I'm calling them they are dropping my calls. Iam stressed because I thought I was done.