Yes. I am very sure dialing 789 is free from anywhere. That's the same number you dial to check your balance. The automated answer picks up and tells you your balance, then it tells you your options for topping up. Voucher, CC, etc. You choose 1 and it asks for the 16 digit voucher#, and credits it right away. I have topped up several times mostly from outside the US.

From their website, under call costs while roaming, it clearly states 789 is free.

http://www.virginmobile.com/mobile/service...ff_coverage.jsp

Hmmm, I'm not seeing that. It just says "Our team via +44 7953 967 967: Standard call rate from the region you're in" - I guess I'll just have to try 789 and see if it works (and if it shows up on my bill).

On the PAYG side, click on "find out more", click on "tariff, then below the cost for each country, there is a table titled "other Call costs"

As I mentioned above, that's the same number you call to check your balance. It would not make sense for it to be a chargable call.