Unable to activate iMessage since recent iOS update, outside of USA. Help!

I am currently studying abroad in Athens, Greece.

iMessage has been working fine, that is, until I updated to the most recent iOS 6.1 software a few days ago. Since my iphone rebooted, my iMessage simply will not activate. It either says "waiting for activation" indefinitely; or, if I toggle the off/on for iMessage a few times, it says "an error occured during activation. try again." I've tried pretty much everything suggested in various forums without luck, including the standard.. turn iMessage and Facetime off, reset Network Settings, then turning iMessage and Facetime back on again. I'm running out of ostensible options.

Might this be the result of my being outside of the United States, with an American carrier (verizon), trying to activate my phone from somewhere (Greece) not authorized to facilitate such activation? Just an idea. Any help would greatly be appreciated, since it is my main form of communication while abroad.

Thank you in advance for any input/advice/ideas/assistance.

-Mattimore