Modem not getting updated speed after upgrade

I made changes online to my service that included moving to a faster speed tier. My customer owned modem restarted during the upgrade process, but it has not picked up the new speed even after several power cycles and restarts. I tried asking through the assistant chat, and they could see two modems on my account. A previous old one, and my current one which replaced it years ago. When I look at my account online, I only see my current modem listed. I'm concerned that the provisioning for the new speed might be getting directed to that old modem that they could see on my account instead of the current one. I could not get the assistant chat to understand any of my questions about this. Anyone have have any suggestions short of going in to my local Xfinity store tomorrow and trying to talk to a real person? 

Thanks,