Billing issue

Disgusting service from telkom. I signed a package for 24 months fibre line rental (10mbs). I have been paying the same amount for until last month. My invoice for this Month is now increased and my package was changed without my authorization. I did not request the package that they are now billing me for and I cannot afford it. When I call them to reverse it and restore my old package I am not getting anywhere with the call center agents. FRUSTRATING!!