Phones that can be unlocked: Iphone (2nd gen, 3G, 3Gs, Iphone 4), Samsung, LG, Blackberry, Sony Erickson, Pantech, HTC and almost any phone that uses a SIM Card.

Many service providers lock your phone so that you cannot obtain service on that particular cell phone through any other provider. For those who do not know how  to tell if their phone is locked, just put a SIM card from another provider into  your phone and turn it on. If you get any type of message stating the phone cannot access service, your phone is locked.

What benefit is there to unlocking your phone? If your phone is locked, you cannot access service with  any other provider. This can be especially frustrating if you are traveling and
trying to avoid roaming charges or if you have a good cell phone you still want
to use and want to switch your service to a different  provider.