How do I deactivate my iPhone?

Are you going to port the number? That would cancel the account for the iPhone, as would just upgrading to a new iPhone with the same account. At that point, you can just keep on using the old phone as an iPod touch device. You don't need to do anything to it, the account is inactive on that old phone, so it cannot connect to the carrier's network. Since it is (presumably) already activated in iTunes, you'll still be able to sync it and so forth.

I pulled out the SIM on my old 3Gs after AT&T had moved my account to my iPhone 4 and have been using it fine that way as a iPod touch. But SIM in or out shouldn't matter. You "may" need the SIM if an update goes south and you need to restore, and you will need the SIM if you want to activate it as a new device (say, on another computer or copy of iTunes).

P.S. I did turn on airplane mode in my 3Gs and then enable just wifi - I wasn't sure if the phone radio would waste battery trying to connect to a cellular network periodically.

Message was edited by: Michael Black