Dual IP Ownership

I've been down for the last 30 hours and have submitted multiple tickets. The root of my issue is seemingly dual IP ownership with another customer. The only way I've verified this is by removing power from my modem and watching our external monitors. Not a single ping drops to the IP address that should be assigned only to our modem.

The modem is in bridge mode, and none of our equipment can communicate past the modem. Talking to level 1 Techs on the phone, it doesn't appear that the modem can talk out either.

The tickets I've got have been escalated, and I've yet to receive a single phone call in 24+ hours.