pwalker 2359, what exactly do you mean by blocked? Do you mean the phone was "locked" so that you couldn't install a local SIM card? Even then the phones would still have worked, but ATT would have charged an outrageously high rate for roaming service.
We've used our ATT iPhones in several countries in Europe. The thing is, ATT does not operate cell service abroad. What they do is contract with other local service providers in those countries, and automatically link you to the most appropriate service wherever you are. But you have to have activated one of their international plans, the most common being the $10/day plan for each day you have the phone turned on. The strategy there is to minimize using your phone at all, or sticking to wifi for communication.
But if you plan to use it a lot during your trip, you could buy a local "burner" phone to use while there, noting that that will give you a european phone number while using it. Or get a local SIM after you get your phone unlocked before the trip.
Good luck