POOR SERVICE AND BAD ATTITUDE

I got an account from MTN of almost R2300. I dispute the amount & the whole account as such. i wanted an itimised bill to investigate myself but i must contact call centre, I went to 3 branches of MTN already and they told me they cant help me i must call the call centre. The call centre is inactive. The last 3 days i spent almost 5 hours on the phone trying to reach someone at the call centre. They just dont answer their phones. I complained to the Canal Walk branch & mr. Howard Green told me they will cut my line if i dont speak to the call centre!! What the hell can i do