Modem Suddenly Not Compatible?

I have never had problems, although I will admit my speeds have never approached 1gbps.  I assumed this was just garbage service from xFinity.

I live in Houston.  We got our electricity back on Wednesday, and Internet service soon followed.  However, since the storm, my connection drops often, and I have to power off and reset my modem constantly.  I contacted tech support via chat, and they told me that everything is fine, but that I need a new modem because mine is not compatible with xFinitiy 1gbps service.   He said that the DOCSIS 3.0 does not support 1 GBPS.  Supposedly my modem is only compatible for 450 mbps, which is about the speeds I get.    Now he is telling me that because the modem is the problem, it will cost me $99 for a tech to come out.   I did not have ANY problems before this ice storm, and I do not believe in coincidences.   

The box of my modem says it is DOCSIS 3.0 with 1GBPS speeds.  So is the xFinity tech lying to me, so that I will buy the xFinity modem, or is he just stupid?  At this point I would drop xFinity if there were any other options but they have a great monopoly so I am stuck. 

Modem:  Arris Surfboard Model SVG2482AC