DISHONEST SERVICE FEE

I cancelled my service with Telkom in November 2023, which they only acknowledged in January 2024 and invoiced me for a further two months. I then received a FINAL INVOICE for -R846.72. They requested so many forms and documents and proof of payment, letter from my bank etc, which I sent immediately. I now received and invoice for May 2024 with a SERVICE FEE CHARGE of R846.72 making te balance R0.00. They took 3 months before cancelling the service, which I was charged for, then another 2 months which they acknowledged as a credit, and now it becomes a service fee??? This does not sound like honest business to me