I haven't bought that way but I just wanted to add, every time I use my citibank card online through overseas sites they have trouble authorising it. If I use my westpac MasterCard, I have no issues. For some reason citibank cards have issues when using them on a site for the first time. They always have to perform checks on it which sometimes involves refunding a small amount and me confirming the amount etc. I try to use my other card where possible to avoid these delays.