I've never heard of recipients being charged depending upon where the call comes from, either with or without Google Voice. Sure, it might use his minutes to be talking on the cell phone (depending upon his plan), but I've never heard of anyone being charged for receiving a long distance or international call. But I learn something new every day, so the fastest way to tell would be to have him check his cell phone usage on line (if his carrier provides that capability), or have him contact his carrier with that question. I sincerely doubt he's being charged anything more than his usual minutes.