trying to change cellphones, Smart card not registering

Hi guys I was wondering, I currently have a Samsung SGH-A727 under AT&T and I jest bought a Sony Ericsson W580i on ebay that is unlocked. When I put my smart card into the Sony it isn't registering. I was wondering if anyone had any ideas.

Did you put the sim in correctly? Also, what does the phone say when you put it in? Invalid sim or no sim. If it says invalid sim then the phone is not unlocked. If you it says no sim there may be a problem with the sim or with the phone.
And lastly, maybe the sim does register but the phone does not have the correct frequencies to operate in your area, so nothing will happen.

If you continue to have problems, I would go ask the store about some help .

The way the sim card sets in a w580i is different than most phone models. You need to make sure it clicks all the way in place, it has a spring inside that pushes the sim card about 1/3 the way out if it's not fully inserted. Unless you have fingernails you will prob need to use a pen to push the card in until it clicks.

If this is not the issue I would try inserting a t-mobile sim card in the phone and if it works then the phone isn't actually unlocked.