Originally Posted by Mr. H
The iPhone will be locked so you won't be able to use it with any other GSM carrier in the U.S. So ending your Cingular contract would be pretty pointless.
It is always possible to unlock a phone. There are very valid reasons for having your phone unlocked. Your carrier always has the unlock codes for your phone. They may not be willing to give them to you, but they have them; and eventually, the codes get out.
Now, are you going to be able to sign up with Cingular in June to get the iPhone, get the unlock code for the phone, and cancel your plan the next day so that you can put the phone on T Mobile's network? Not likely. Would you be able to do the same in June 2008? Very likely; though I don't understand why you would.
And if you have been a Cinglular customer for a number of years and have a valid reason for asking them to unlock your phone (You will be on a school exchange in France for three months and don't want to buy a new handset to use over there, for instance), then Cingular will likely be quite happy to unlock your phone. The reason that they give you a locked phone is so they're not subsidizing their competetors, so if your history with their company is good, they have nothing to fear.