can I use my old ATT/iphone sim card in a new iphone?

No it will not work.

Certainly it will work. That is exactly what happens when an iPhone is replaced by Apple at their store.

What's wrong with your current iPhone that you want to replace it?

Neil

iPhone to iPhone may work. The other day when I was bringing a sim from a Treo 750 to iPhone it definitely would not work.

May I ask you why think it will not work?

When you do things that are not designed to work, they don't.

NYCAMS,

If the SIM card was originally activated with AT&T on an iPhone it will work, but you may need to connect it to iTunes for the iPhone to confirm its an active SIM.

Hope this helps,

Nathan C.

kmosh100 wrote:
No it will not work.

Could you tell that to my SIM that worked...

Willliam

Apologize -

Mis-read original post to read to take an old AT&T, pre-iPhone, SIM in an iPhone.

My mistake.

Of course an SIM already used in a previous iPhone will also work in a different iPhone.

If it's an AT&T or Cingular (whatever) SIM card it will work. I first activated my iPhone with my old SIM that wasn't 3G. Then I switched bc obviously the 3G SIM card was faster.

Work means that everything works.

If it were the case that everything works, why would any previous AT&T user need to activate the iPhone.

All that would be necessary would move the SIM. I do not believe that the AT&T/Apple relationship left that back door open.

You have to activate the iPhone because you have to active your iPhone account. This isn't just another phone that you can switch SIM cards between and it work.

I don't know what "back door" you're talking about but I hope that you would know by now the iPhone is not another regular cell phone. But it most certainly does work with any AT&T SIM.