[Cryptography] phantom 3g service?

[Ray Dillinger]

So anyhow, since 3g service has been terminated in my area, I've kept my 
old phone because it's still fairly useful as a wifi device.  Can't do 
voice talk or SMS any more since I transferred my phone number, but it 
still does everything else.

Thing is, sometimes when I'm walking around, it thinks it sees 3g 
service.  And I airplane-mode the thing and stick it back in my pocket.

There are exactly zero carriers in this area who still provide 3g service.

Are these obsolete stingrays?  Scammers fishing for people who still 
have old phones and now can't get legit service? Or something else?

Bear