They sell them factory unlocked in Ellada?
Doing a quick search and I found this...
While Verizon sells Apple's next-generation smartphone at full price already unlocked out of the box, that is apparently not the case with AT&T. Normally, AT&T customers who opt to pay the full $649 price instead of agreeing to a two-year contract for a subsidized iPhone must follow a lengthy process to get handset unlocked.
Those AT&T customers must fill out a Web form, send a fax to AT&T, and wait as long as a week for word on whether it will allow the device to be unlocked.
However, it now appears that unsubsidized AT&T iPhones ship unlocked and that off-contract customers can save a lot of hassle and time by simply restoring the device in iTunes.
This little bypass was first reported by Tech Crunch, which says it confirmed the process with AT&T technical support and successfully reset an iPhone 5 with a T-Mobile SIM card, getting the usual unlock message: "Congratulations, your iPhone has been unlocked."
iPhone users can confirm the unlock by swapping in another GSM-compatible SIM card, Tech Crunch's Romain Dillet explained:
AT&T's off-contract iPhone 5 can be unlocked with an easy reset | Apple - CNET News