You need an international sim that does not have any restriction. I
personally carry United mobile/riiing and and IOM sim sold by
freeglobalsims. I have used these sims in several carribean countries,
Mexico, Nigeria, UK, etc. without any problems. Another new card that
works in more countries is yackie. I have it, but have not fully tested
it.

United Mobile:
http://www.united-mobile.com/cms/web...2&idcatside=26
GlobalSim: http://www.freeglobalsim.com/
Yackie:http://www.yackiemobile.com/


You may want to check out the international forum here for more info:

http://www.prepaidgsm.net/en/international.html