First, thanks a million to those who offered tips! I am at this very moment typing this on the Netwalker, connected via the celular modem:
I got it working!!!! Here is what I did.
Besides selecting my proper country and celular Internet provier,
1. In Terminal, type sudo gedit /etc/resolv.conf
2. In the file that opens, change whatever it says DNS-wise to:
# Generated by NetworkManager
nameserver 208.67.222.222
This is one of the 2 OpenDNS numbers I discovered on the Ubuntu Forums. The other is 208.67.220.220. It may also work with other celular modems. It also worked on my desktop Linux box.
Hope this helps somebody else!
Dr. Steve, central old Mexico