TELKOM TERRIBLE SERVICE

I am completely disgusted at the service recieved from Telkom, my services have been cancelled due to issues when the changeover to LTE was done. i have cancelled and yet still was billed even after cancelling. Spoke to agents and they have confirmed cancellation in order but yet i recieve invoices for over R4000! now this is giving me a bad credit record. I needed this sorted out asap, who do i contact??