Billing 3 months after cancellation has been made

I cancelled my internet and adsl line with Telkom, filled in form and sent back as they requested. I got a call saying all has been received it will take 30 days to process, so my second invoice from date of cancellation will be just my phone line. I cancelled in october 2015. I a am still receiving invoices with full charges for adsl. I queried this and they said not to pay until a credited invoice comes through with my actual amount due. So in return of me waiting and not paying they have cut my line completely and now not able to use internet with my current ISP. Last 2 weeks after visiting a TELKOM SHOP. I have been told they will call me regarding this matter and still no response... This is the most useless company i have ever delt with and its a pity we are forced to use them.