I purchased 2 iPhone 6s plus' via the Apple site a few days ago. They have a mid October delivery date. I plan to just keep my eyes out for any that come into stock in the meantime (if it even happens). If I should find 1 or 2 before my other orders arrive will I be able to purchase them and then return the others when they arrive (or just cancel the order if not shipped)? Is there like a limit of how many can be purchased?