CM500 existing MAC address

I've been using the modem for over a year without issue with my prior ISP. A month ago I switched ISPs and while trying to activate the modem, I was told that a modem with the same MAC address was already in use and would be unable to activate unless that other user deactivates first. I've tried contacting Netgear support and have a case number 43435698, but was unable to progress in the call because I was outside of warranty. As a manufacturing issue that I unfortunately didn't find out until I tried changing ISPs outside of my warranty, I'm hoping that there is some way that I can still get some help.