Customer Service

Every month I receive an astronomical phone bill between R5000 and R6500 a month, no one can tell me why, no one can provide me with a billing report. I must pay extra for the service when previously at nashua mobile i had it in my contract, I got transfered to altech autopage because nashua mobile was sold, now I must pay extra for a service I was already getting, I find this unacceptable that I cant see why my phone bill is so high but i must just accept it and pay?