Poor service from Telkom

I took a contract with Telkom and to their error I was given 2 devices, I returned the second device unopened and everything sealed within 5 days and it was excepted. A month later I am being billed for the second device that is returned and despite all the engagements we had and my query being resolved I am still getting my account being debited. This is disappointing from Telkom that I have to be entertaining my account being deducted and causing unnecessary charges to my account