New Bulk Community Internet Unstable

My apartment building switched to Bulk Contract Community Internet about three months ago. About a month ago I moved into a larger apartment (about 2,800 square feet). The internet in my office (about 150 feet from the modem) has very unstable internet - my Zoom calls drop 7-8 an hour, my browser often stops responding and I am frequently disconnected from WiFi. I have tried all the troubleshooting steps multiple times through the AI chat, the human chat, the AI phone, and ha on the phone. I have had two technicians come out to tell me there is nothing they can do. The first had never seen my type of modem before and told me it wasn’t an Xfinity modem (even though it was installed by Xfinity through the bull contract). I was given a phone number to contact bill support 1-855-307-4896. They sent a technician who they assured me was a bulk technician and was familiar with the modem. The technician who came had also never seen the modem before and was not a bulk technician. I am at wits end. How do I reach someone who can actually help me? I am locked into a lease that requires me to use Xfinity Internet (which I have to pay for $70/month for) otherwise I’d move or get a different provider.