Out of 36 posts (minus all the posts about my reply) only 3 posts actually made some attempt to offer the OP any suggestion (not counting buying a different device)
I've had my Passport since the day it was released! I briefly had the same issue as the OP and the very few others of you that still have this problem.
It took me several hours of searching and investigating and it took EXACTLY what I posted to get my Mobile Network back up and running.
I see a lot of "maybes" " ifs" and so on, but not one hint of anyone actually trying my suggestion.
What if Maybe you give it a shot ? Whadaya got to lose??
IT WORKED FOR ME!! And I'm no different than you guys. (Well, I Am special....) but other than that......
http://www.picturesanimations.com/3/3d_smileys/0251.gif