Comcast is a joke.
I have used Netgear modems for years, and I can assure you the problem isn’t with them. Last year they, Yfinity, offered me gig speed, only to slow down my connection from about 550mbs to 270. Then they told me that even though they lied about their promise to us, the "package" we had was no longer available, so we’d have to switch to a more expensive plan and live with the slower internet speed. ps, I live in FL, your state may differ in what they allow the cable companies to do to their citizens.
Of course, having dealt with them for decades, I recorded all of my conversations with them, and at the end started to play the earlier promissory recordings back while I was talking with customer service. (An apparent code phrase for taking care of the livestock.)
We cut the cable cord, and they haven’t asked for their boxes back yet, and are charging us less than the price of our now correctly charged 250 speed.
So, how to slay these demons? First, they may insist they be involved with resetting your modem, but you can do that with your modem app or through terminal/web browser…. But you can also do it the best way: Disconnect the cable and all other connections to the router, including power. Depress the power button for 30 seconds with no power connected, doing a clean state reboot, then reconnect the modem and attach the power and turn it on, giving it a minute or so to reboot.
I have found that this always solves any problem that I am financially responsible for.
I hope this helps, regardless of brand.