The worse network provider ever

The worse network provider ever. I signed up for the router 101 which was a month to month but they act as if it's a contract now the credit keeps on increasing every month even when the router is offline. This is the 5th month requesting for cancelation with no help. Now they say i owe them R3150 for something I'm even using. They must collect their router and clear my name for good, I don't owe them and i don't understand how it keeps on increasing whereas it is a month to month thing