I live in Michigan and I couldn't receive any calls from Michigan while I was in DC. Got all the calls from people in DC.
Go figure. I didn't try it while I was there but I should have had someone in Michigan dial the area code and the phone number to see if it made a difference.
That shouldn't be necessary though.
P.S. iPhone saved my butt in DC. I have a TomTom One gps unit and the POI's were a little lacking. Using google maps to locate a destination and then putting that address in the GPS unit gave me a direct hit every time.
I started destination every search from Google before going to the GPS unit. Perfect.