...Does it depend on what service you have? My boyfriend is currently out of the country for a month and says he can't talk to me on the phone because his cell phone would cost more to talk on the phone. He uses T-Mobile, but I don't think he is sure about this.

I'm with T-Mobile,
Calling from abroad cost more than normal rates, but it does depend on the network.

And your plan as well...Most plans have free "Nationwide" calling. That applies to within the USA tho. There's always email! :-p