Telkom accounts nightmare

I have had a 2MB uncapped service with Telkom for years, always paid R700pm, this means we where in credit, then I upgraded to 4MB uncapped, the agent upgraded the line and then failed to cancel the 2mb uncapped service. It does not matter how much you argue with them, they say I am now in arrears almost R2000, Eventually they cancelled the 2mb service and then cut my line off!!!!