The Apple rep told me that I needed to cancel my order instead of switching it, which was fine. But it turns out that you can't pre-order a sim-free iPhone on the upgrade program. My only option is to go into the store and do it there.
Sort of bullshit, I may keep my 6 for awhile longer, it seems.
Sort of bullshit, I may keep my 6 for awhile longer, it seems.