Rain robbing customers

I’m on month to month subscription with Rain for more than a year. I did not pay since January and I was automatically disconnected. Now I receive a billing that I owe them 1800 and I called in to ask what is it for and the lady that called was very rude and says I was connected and I used the Wi-Fi. I want to know how as the router was was even off the plug for almost 2 months