I'm assuming you're talking about buying from the boutique itself?
It depends very much on which store you're buying from, and how your relationship is with that store. I know most stores will not ship internationally for customers they do not know / know very little about, but if you are a regular (whether you always shop in person or over the phone) then perhaps the SA might be willing to bend a little for you.
Generally though, they don't sell Birkins over the phone.