Same thing happened...phone would default to XNet when I wanted to use my WiFi card and I had a few small charges...called them up and whamo...no more data with minutes.

They said the only way to prevent this was to take away my Nat Access part so I did...phone still works, WiFi still works.

Looks like I need to look back into Quick2Net.

They told me the same thing and I talked to three different people and a supervisor...blah, blah, blah.