Greetings, @Delosiv! Thanks so much for taking a moment out of your busy day to leave a post on our community forum. I'm sorry to hear you're still having issues with your service, but you have definitely come to the right place for assistance.
If you could send me a private message with your full name, and the name listed on the account (if different), I'd be more than happy to look into this for you.
To send a Private Message, please click on my name (ComcastJamesH) and select “Send a message”.
Either NetGear or Xfinity is lying!
It is Comcast that is responsible for updating the firmware of combo modem / router gateway devices.
If you obtain a solution, please post that info here in the open forums so that all readers here may benefit from the exchange. This is in keeping with the spirit of which these public help forums were originally intended. Thank you. @ComcastJamesH