Bad service

I signed up for month to month contract with Rain. Meaning when I don’t make a payment on a certain month they cut the internet…I haven’t been using their internet because when I didn’t paid they cut it off…now they say I owe R1900, my rooter has been off, I haven’t been using their internet as I didn’t make payment, how come I am owing that amount for the internet I didn’t use. I spoke to an agent, she promised to send proof, I have not received it to this day