BAD BILLS

I logged a dispute with telkom in last year for the fact that the over charged me 4 months later I get a call resolving my problem, Now I get a call from them saying if i do not pay in 2 days my line will be cut of so i asked the call centre agent in PE to tell me whats my bill she said R382.28 now i receive my bill for this month and its R1503.95... How the heck are they billing people do they just guess ok we bill you this amount i am now fed up with them i phoned and asked and all i get is you must pay us this or we turn of the net .... I asked them to call me about this matter but no one called me or emailed me