Complaint about telkom

I had opened a contract with telkom wanting a router but a wrong device was delivered then I took it back to the store they took the device back and told them I want nothing to do with them,I don’t even want the correct router anymore,but strange enough money was debited from my account this went on for 2 months but every time I’d reverse the money.whenever I’d go to the store they’d promise that they are sorting out the matter till today,just last month I went there at eastgate mall then I was told the reason they billed me was on the system it didn’t show that I’d brought it back,so I got a case number and the guy said il receive communication beginning of the coming week indeed I did get a message stating that the case has been resolved.soon after that I received messages from the legal department threatening to send a letter of demand and that they have handed the case over to the attorneys.i really don’t know what to do anymore the money keeps on increasing.