99, or went to Amazon...99, and use my gift card (like a credit card?) to pay for it. I also heard that if I wanted to purchase things online, I have to register on American Express's website for a billing address(such as my home address), my name, and a few other details. Hi, I recently got a $25 American Express giftcard for my birthday, and i've heard that you can use this card to purchase things online. So for example, if I went to buy a game on Steam for $19.com and bought a book for $19. Will american express send a bill through the mail to my home address each time I purchase something? Such as telling me that $19.99 has been deducted from my $25? Or are they asking my address for promotions and such? Thank you for your