I have taken my cell phone a few times and it was worthless (east side of the Sierra). I could not get anything, yet others could. I was told it was because I had AT&T and they have poor service in rural areas. In this case, does it matter who the carrier is for the "ping" thing? Will a non-AT&T tower pick up my phone? I suspect the reason I do not get service is that AT&T simply does not have an agreement in place with the local carriers. Or that I have a poor plan that limits my roaming capabilities.