Problem with purchase of audiobook, via Iphone Itunes

Hi All,

Just got my Iphone, and have made my first purchase on it in the Itunes app for an audiobook, clicked on the buy button then password, but then it said that i need to either have wifi or download it via itunes as over 10mb, does this mean i have purchased it and will be charged or does it cancel it and have to click buy again on itunes or when im in a wifi area, or have i bought it and just need to find where i download it on itunes.

sorry for so many questions just dont want to pay for it again if i have allready bought it.

Thanks inadvance