I can't speak for CGK, but when I have used AA's GSA in MNL they have required physical sight of the credit to make the purchase. Elesewhere in the world in the past I have got them to accept faxed or scanned and emailed copies of the card. But I think you are quite unlikely indeed to be able simply to give them a CC number over the phone to do this. Wire transfers are also a possibility with some GSAs.