Complete Xfinity support failure.

My internet keeps dropping and after several calls (which the chat bots said there was a problem but was resolved) the problem is still ongoing. I managed to get a tech out to my house and by chance the problem occurred while he was here. He diagnosed it as a bad modem but said he was unable to replace it (because I have Xfinity NOW and I have to replace it!!!!!). How do I replace an Xfinity provided modem????  When I rated this support as a 0 (because Xfinity both could not and would not fix the problem) a customer rep called me, said tech support would in fact replace the modem, transferred me to them, then they said they had to transfer me to another group who does equipment replacement. I was then transferred again to someone who said he was with “boost mobile”.  He said he had no idea why I was transferred to him, and that he couldn’t help me, nor was he able to transfer me back. ….xfinity has so far provided the worst support ever.  Is anybody there able to work through Xfinity’s abysmal support process and do what a support group is actually supposed to do?