slow internet speeds

I thought I would try here since the actual Xfinity customer support is absolutely abysmal and forget ever trying to connect to an actual live person. I have the 2 gig package and everything has been running fine as far speeds for the last two months until the last two days. Since then, I've been averaging 90mbps. After numerous tries with the assistant and a text round confirming the signal input is fine, they seem to dumbfounded and all they offer is to upgrade your modem. It's obviously a signal problem on the Xfinity end for which they seem to not want to do anything about. Right now I honestly feel like I'm being ripped off.