This will probably be my final update to this.
I got my modem replacement in the mail, hooked it up, and like others in this forum, discovered that it was configured to connect as a Bell modem and my v2xxxxx##@virginmobile.ca username couldn't even be entered into the internet configuration. So, another hour on the phone with Virgin support, and they say I need to exchange the modem again. I schedule an appointment at the local kiosk, and exchange the new modem for a newer modem.
This one at least allowed me to enter my username, but then I repeatedly received an "Error 2000: Unable to connect to Bell servers" message. Thinking that partially functional internet is better than no internet, I try plugging my original modem back in. Now it gives me the same error message... along with a Bell Technical Support phone number, which I call.
This was, at last, somewhat useful. The agent I spoke with looked into my account and said "something strange is going on here". After a bunch of searching, he discovered that the ONS serial number listed in my account did not match the serial number of the SFP module that I had in the modem. After some work, he managed to correct it, and rebooted the modem one more time and, lo and behold, I had an internet connection again!
Unfortunately, I was so thrilled to be connected at all that I didn't check the IP address. This morning I tried to upload a photo to discord on my phone, and it wouldn't work. I turned off my wifi, and it uploaded in less than a second. So, I logged into Valerie, and checked... I was still being assigned a 10.139.XXX.XXX IP address.
This time, I tried calling the Bell Support Line immediately. The agent I got this morning acted like the Virgin support staff. "I'm going to reboot your modem". I got frustrated. I have changed the modem twice, and spent hours on the phone. Rebooting the modem is not the solution. The problem is that the Bell servers are assigning my account a subnet address that is not accessible to the internet. My modem has nothing to do with the DHCP assignments made by the Bell server in the PPPoE negotiation.
Her response was that the Bell Technical Services division did not have access to the DHCP systems, and that it was an issue for Bell System Support, and that she did not have a direct line to access that division.
I'm done.