If you're worried about accidentally using the ExpressNet, or overly paranoid like myself there's a really easy fix to make sure.
Click:
[Start] -> [Settings] -> [Connections Tab] -> [Connections] -> [Manage Existing Connections]
Select "Express Network" then click [Edit...]
Click [Next]
You should see the number "#777". If you delete this (or as I do change it to the text "Disabled") it will prevent your phone (and friends) from accidentally connecting. I prefer the "Disabled" option because when it attempts to dial it will say "Dialing: Disabled" letting you know why you're not connecting properly.
Also, I should state, I got this idea from someone on this forum a while back. I don't mean to take credit for it. I'm just too lazy to search for it.

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-UNOmar-

"hockey, hockey, hockey..."