You haven't dialed internationally before, I take it? 🙂
From the US, you need to prefix any full number with the country code, and if applicable, city code. All US int'l dialing starts with 011. For example, if I wanted to ring a friend in Melbourne, Australia, I'd dial 011 61 3 9xxx xxxx, where:
011 = international
61 = Country code (Australia)
3 = city code
9xxx-xxxx = person's phone number (in 1995, all local numbers there were given the 9 prefix before the actual number).
So in your case, the number would be 011 50 xx xx xx xx.
my GV number is a standard phone number actually picked from my area! not sure why his would be different! why not have him text call you and just add it to his contact! 😉