I am a heavy user of data and cellular service. The phone was working then the connection began to degrade and then no reception. I have no cellular connection and all the settings are on and correct.
I am in the same predicament! currently using my Q10 while I wait for a solution. There are a few other posts regarding this issue that have been posted by other users earlier this year and in general no one has an answer that works other than to send the passport back and get a replacement =/ I've had my Passport since May 2015 and it worked like a charm till about two weeks ago when I had this signal problem. It's not my SIM, it's the phone.