They don't take orders over the phone if you are not a VIP. The stock varies greatly, usually Kellys are not so hard to find. Birkins are possible to find but you probably have to go more than once and not be to picky about colors. Do a search alot of good info on this topic.
You can never predict the stock. The week I was there (late June), I went to the store every day and only 1 Birkin (a 40 in red) came in the entire week. The next week, according to others, there were alot of Birkins available. It is unlikely you will find your 1st choice color in your 1st choice leather in your first choice size.