Need help reactivating

I recently made a new Xfinity account because I'm tired of this At&t internet. I bought a plan and picked up my modem, and within 2 days the internet was off. Less than a week in, the automated system auto-canceled my new plan and sent me an email telling me to return the equipment. I talked to customer service and they said there was a pending disconnect on it. I live with my father but I am a resident here trying to start a fresh plan under my own name making my own payments. I'm confused here and just want good Wifi please help.