False stolen device claim / blacklisted

I was using an ISP known as Vision ISP, located in Marianna, FL. A few weeks ago everyone lost internet connectivity. Supposedly this guy was selling or reselling internet service (unlimited) by piggy backing off off the FirstNet services ATT offers. 

Many customers (including myself) jumped ship. I came to ATT and opened a business account. It's been fine for 2-3 weeks now.

I purchased my device from Best Buy back in November, I own it, it's paid for.

The only thing this ISP provided was a SIM.

Everyone that jumped ship has had their IMEI's flagged as stolen, and their devices no longer work. Whether they purchased the device from him, or brought their own (like me).

Yesterday my device stopped working, my account does indeed show the device (that is in on my desk) as stolen. Many people have called in and had their device unsuspended only to have it almost immediately show up stolen again.

The ISP is not replying to phone calls, texts, or emails from any customers. We've not heard anything since April 26 (check their facebook page).

What can I do? How can an ISP block a device I bought and own from ever being used on the internet? I had to make payments to buy the device. I use it to run my non-profit animal rescue. We're in a rural area and this is currently the only internet option we have.