is this possible? trading phone with friend?

Yes that can be done. He can upgrade and do whatever he wants to do with the phone.

 

I just traded in an iPhone for a Samsung Captivate. Not sure about your carrier but I asked at AT&T if my SIM would work in both phones (thought it would be cool to switch it back and forth sometimes). They said no. I guess with AT&T the iPhone unlimited and the "Other" smartphone unlimited are two different plans and they are not switchable. At least thats what I was told by the salesperson. Haven't really tried it myself to see if its true.

 

Doesn't the iPhone take a microSIM card? if so wouldn't they issue a std SIM card with the new Inspire and turn off the old one?

 

I had to add another line in order to get the Inspire, I bought a micro sim adapter and just put my iPhone 4 sim into the inspire and works great!

 

it's bs. you can switch back and forth provided you have an adapter for the iphone4's micro sim card. on an iphone 1g, 3g, 3gs you can switch it no problem.

i did it with my captivate and even now my inspire that i purchased off contract (had an upgrade but didn't want to burn considering how cheap the phone is)

 

It was a 3G and they just swapped them out. Now my iPhone just says No SIM. all the time. Kind of want an extra SIM just to get rid of the message. Guess I'm just to lazy to pull it out and switch. Does the battery need to be pulled on the Captivate before pulling the SIM? Wonder if I can just get a cheap AT&T SIM off Ebay and pop it in the old iPhone to get rid of the message without buying a phone plan of anything. Its mainly just used for Skype wifi calls right now. My other VOIP apps wouldn't work without a SIM for some reason.

 

Do what I did. Jailbreak and unlock the iPhone. Then you can use it without a sim. Or I have seen att sim cards on amazon for cheap.