Unfairly billed for an unexciting contract line

I have a contract with Telkom. When it was time to upgrade Mondo the third party that sold me the contract contacted me for an upgrade. Instead of upgrading I ended up with 2 contracts only realised 4 months later that I am being overcharged. I contacted Mondo they said Telkom will cancel one line. They cancelked the old line and said Telkom will refund me. I never received any refund. I continued being overcharged for a router that does not work because I never received a sim card with the new router. I started reversing monthly when Telkom debuts my account because I was not receiving any service from them. Till today I am receiving no service and Telkom debuts whenever they want when there are no funds my bank charges me. I went to Telkom in Middelburg mall. I was told by one of the employees there they will only help if I can pay the outstanding amount. I dont see why am I suppose to pay for a service I have never received. Telkom breached my contract with them when they stopped loading the simcard with data. My credit score is suffering I am being unfairly treated. Can I please be assisted with this matter.