This Saturday Emily's AT&T BlackBerry Pearl contract hits the 1y 9m mark. That means she's eligible for a fully subsidized iPhone . Considering how much we've wasted on the Pearl's underused $30/month data plan this iPhone will be a bargain.
The first step in a phone switch is to unlock the old phone. You may be able to do this after you've switched to the new phone, but it's a pain. Do the unlocking before the switch, your phone will still work normally.
Once unlocked a GSM phone can be used on other GSM networks, such as T-Mobile. If you have a foreign Pay-Go SIM you can use the phone abroad. The unlocked phone will also work on the original AT&T network. (Note that in practice some phones are very network specific, and you'll find some quirks or missing functions on a foreign network.)
I've written previously about (authorized) Nokia unlocking, happily the BlackBerry unlock procedure is simpler.
Here's the procedure for network (AT&T) authorized BlackBerry Pearl unlocking. (See How to unlock the BlackBerry Pearl and enter Blackberry Unlock Codes for unauthorized unlock procedures.)
- Call 611 (AT&T support) from the BB Pearl to request an unlock code. If you're nearing th end of a contract and say you're getting a new phone/contract this is routine. It takes about 10 minutes to walk through the procedure and get an unlock code. You may be asked for the PIN number of your AT&T account.
- Go to Settings (folder with gears) then options (wrench) then Advanced Options.
- Select SIM card. (shows phone number and the unique phone ID)
- Hold down alt key, type MEPD (nothing displays)
- Hold down alt key, type MEP2 (nothing displays)
- You will then see a prompt allowing entry of the unlock code.
- Enter the long unlock code.
- Hit the enter key. If you take a while to do this the unlock code will clear and you have to reenter it.
- A "code accepted" message will flash and the SIM screen will show "Security disabled"
Now you're ready for the phone switch. When you make the switch you can also ask the AT&T store to flash an upgrade to the latest version of the phone ROM.
 Emily thinks I'm going to take the GS and give her my 18 mo old 3G. Don't tell her she's getting the new one, it's a surprise.