Cancelled, yet still being billed

I cancelled my Telkom services in May, and sent through all the necessary documentation in order to cancel my services. My services were confirmed cancelled in June and was assured that no billing would take place. Yet, I spoke to someone in the billing department and they confirmed that my services were cancelled, yet billing continued from July. I was given a TIN number when speaking to the sales department, so that my services could officially be cancelled. Yet, I tried phoning and the lines are always too busy...At the same stroke, my credit record is being negatively impacted for something that's not my fault. Please correct, resolve and remove from ITC!