Phone won't work in JFK Airport!

This is the oddest thing. My phone shows 4 bars of service, and I c an connect to the Terminal's WiFi network with no problem. I can surf Internet, and send text messages. But 100% of the time that I am in Terminal 5 at JFK Airport, I cannot make or receive phone calls! I see all the people around me talking, but I can't. I've tried turning phone off & on again, but to no avail. Calls TO me go to Voicemail, but I do not get any notification that I have voicemail until I leave the terminal building.
As soon as I step out of the terminal, I can make or receive calls. When I board a plane, I can make calls.

This does not happen anywhere else.

What's going on?