I haven't read every post, but my experience is different. I went to the Apple Store today. I preordered there. After I walked outside, I realized I had not specified 6s or 6s plus. So I rushed back in to the store to change my preorder. There I discovered a couple of things. First, my preorder is not shown in my account, nor does it have a number. Nor did I give a credit card (although I have a credit card associated with my iTunes account). The only thing I got is an email. Now, I had them ship for pickup at the store. They set up an appointment time to pick up at 2pm on the 25th. The associate told me I could set payment up at that time. As you know, there's a number of different of different methods to pay, one of which is the Apple plan, which they were unable to fully explain, training on that has not started yet. Anyway, I had ordered unknowingly the 6s. So we tried to cancel or change the order. That can't be done. It stated that in the email. So I told the associate lets place a second order for the 6s plus. That couldn't be done either, it was not available. They told me I could switch when I picked up, assuming what I wanted is available in the store. That seems like a slim possibility. The other thing I found interesting is that one of the options to pay is to pay cash. But at least as of now, it is not unlocked if you buy that way. The only way to buy unlocked is to use the Apple payment plan. So, just throwing it all out there. Right now I have an appointment to pick up the 6s 128g on the 25th, only confirmed by an email.
