If you have an older iPhone and are eligible for an upgrade, you can order the newest iPhone directly from Apple and pay only the subsidized upgrade fee without ever having to step into your carrier's store. Here's how to do it.
Part I. The Upgrade
Assuming that Apple announces new iPhones on September 10, the company will almost certainly announce when pre-orders can start online at Apple.com. If you have an iPhone that's eligible for upgrade from your carrier, for example AT&T or Verizon, you don't need to visit your carrier's store or logon to your carrier account.
Instead you can order directly from Apple online, which is probably a better bet because Apple will likely have the best availability of the iPhone you want when pre-orders become available.
The way it works is this: when ordering, you'll be asked to enter the phone number of your eligible iPhone. Apple's online ordering system will verify with your carrier that your phone is eligible and will then present to you the appropriate charge. In the case of AT&T, this will likely be: US$199.99 for the current 16 GB iPhone, sales tax for your Zip code, and possibly a $36 upgrade fee. You'll also be asked to check a box agreeing to a new two year contract.
While you're waiting for your new iPhone to arrive, it's a good idea to back up your old one, either to your Mac or Apple's iCloud.
Once you receive the new iPhone from the friendly FedEx driver and activate it, the new iPhone inherits the phone number of the old phone -- which is then deactivated. The activation process is straightforward; the iPhone will walk you through it. Using the backup you previously created, you can then restore your apps and data.
Finally, you may wish to have the carrier unlock the old iPhone, and then you could press it into service with some other carrier. Or sell it. (After you completely erase all your personal data, of course.)
Part II. Wife Swapping
If you're like me, you always have the latest iPhone and your spouse always has a two-year-old iPhone that's eligible for an upgrade when Apple announces a new model. After completing the process above, that old iPhone is deactivated and the new iPhone (5s, 5c) is now activated and working on the same, original number.
At this point, my spouse and I swap phones. (After all, if I'm going to write about the latest iPhone, I have to own one.) We can do that easily because we keep our iPhones in pretty much the same configuration -- except for email. She would get my iPhone 5 and I would get the new iPhone 5s. How do we do that? Simply by swapping the SIM cards. That's possible if the iPhone 5 and its successor use the same nanoSIM, and we, at TMO, think that will be the case.
Swapping the SIM cards is all you have to do to swap the phones, but if you do run into any difficulties, you can call your carrier or visit a local carrier store. However, with long lines right after Apple announces new phones, you may have to wait a few days before you can actually go in and formalize the swap without having to wait too long.
The reason you may need to visit the store is that once an AT&T SIM is deactivated it can never be reactivated (at least not in our experience). If you anticipate being short a SIM – or simply want to hedge your bets – visit an AT&T store before release day and have them give you an extra SIM or two. They should do this for free, especially after you explain why you want it. Feel free to insist. Then when you're on the phone with an AT&T rep, you can do everything at home without having to visit the store on launch day.
iPhone 4S teaser image via Apple