Forcing me to use Comcast modem

I live in youngstown Florida in the neighborhood where the recent Tornado outbreak took place. I went 27 hours without electricity and cable. When it did come back on everything seemed fine for a few days. Now all of a sudden xfinity swears I have an issue with my modem. I'm supposed to call the manufacturer and complain.  My equipment is fine and working properly.  And get this, the whole time I'm trying to get the signal needed to operate xfinity is trying to sell me a modem and use their equipment.  I'm really upset. I work from home. I've already been down one day without internet to pay my bills. Xfinity what are you going to do to get me back up and running so I can pay my bills. I work from home.