Ok, so I think you did completely unrelated things to get the thing working. First, your initial problem was likely the lack of a proper usb_modeswitch rule to get rid of the builtin drive. Next, you should have just tried using ModemManager along with NetworkManager. Actually, you say you ended up launching a wvdial script and then connect through GNOME’s UI, yet that is impossible :) What likely happened is that once you got the drive unmounted you got the proper AT ports to play with, and ModemManager started to play with them right away, which is why you could see the mobile broadband connection icons in gnome-shell. So, all the wvdial stuff was totally unnecessary.
If you have problems getting modems detected by NM/MM, get ModemManager debug logs, and report the issue to the ModemManager mailing list in freedesktop.org… that is actually “the right thing” to do ;)
Cheers!
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