They wont accept Fairfx as it isnt a credit card or debit card.
How has he paid?
I got mine through Virgin Holidays prepaid with a debit card for the platinum package and didnt have a problem, but if you havent prepaid I think you will have a problem, they will see it as a cash hire and will want something like $500 cash as well as the rental price. You then dont get the money back until you return as a US cheque which is difficult to deal with!