Suggestions On Cell Phones/carriers For Studying Abroad?

Hello everyone,
My brother is going away for 4 months to Belgium this summer for a study abroad program. For his trip, I want to make sure he has a cell phone, but I’m not sure where to start searching for a reliable and legit service. Do any of you know of any services/carriers that offers a reasonably priced international service – preferably one that has low or free calls to and from the US land/cell lines? I had AT&T unlock his iPhone so I have the option to get a SIM card instead of a whole new phone. My last option is to go with the ridiculously priced international plan from AT&T, so any tips, advice, or recommendations are very much appreciated. Please leave a link where I can get more information. And thanks to you all in advance!
Thanks,
Steven

Incoming search terms:

• sim only carriers (1)