taking my iphone to europe?

[E5'sWife]

i'm going to europe soon and i want to take my locked att iphone and switch the sim card with an european sim. how do i do that? do i need to jailbreak it first?
i have 2 iphone 3
i have their imei codes and they wont unlock them, just called them :/

 

[4foneecom]

Need more info as not all iphones can be unlocked. Is it iphone 4 or 4s maybe 3gs?

 

[jjpeter11]

I'm recommending you to buy holidayphone sim card for your international trips. It is very cheaper and best international sim card.My friend suggested me this last year. You can refer all details here SIM Card for United Kingdom . Happy journey.SIM Card for United Kingdom