I'm wondering about this, too. Could be because their supply chain is so unpredictable that they don't want to get into making future appointments? Every model/carrier I was interested in was sold out for 09/25 appointments and I'm like why can't I make an appointment for a few days later? Makes me wonder if the Upgrade Program is a Day 1 special or something.How do I reserve to buy iPhone 6s in store for a date other than 8/25/15? Say, for example, I want to buy in store on 8/28/15, since on 8/25/15 the store I want to buy from does not have the iPhone 6s model I prefer? Is there a way to reserve on a different date?