On your very first purchase you have to verify your phone number.
They will give you a call at that number (it is an automated voice message) they ask you to say yes or type in a number (I can't remember exactly it was a long time ago). Then you should be able to place your order on their site. Because everytime you go there you need to enter in that same phone number you just used. Then they can give you a 5 digit number that lasts only 24 hours to make a purchase from their site.
The phone that you are using must be sms-enabled to get this code!