Please suggest do unlocked cell phones work for all cell phones?

The Subscriber Identity Module (SIM) card is the little piece of plastic that identifies your phone to the cellular network. Changing your SIM card to have your phone work on another network is especially useful if you want to travel to another country and want to buy a pre-paid SIM card so you can have cell phone access without roaming charges. The SIM-lock, and network code, net code and restriction code (Nokia), is a term used in the mobile telephony sector and describes therestriction of usability of the mobile device on SIM cards that meet certain criteria. Typically when you purchase a cell phone, the company that sold you the phone (ex: AT & T) 'locked' the phone before you bought it, so you can only use it on their network. Currently, mobile phones can be locked to accept only SIM cards from certain countries and/or providers and/or networks and/or SIM types. This means that you cannot use your phone on any other network, even if you change the SIM card. Almost exclusively in prepaid packages, T-Mobile temporarily activated in many contract mobile phones also Netlock. In Austria, the SIM-Lock in contract mobile phone is always on. Occasionally, however, that devices - as externally purchased or because they will quickly come to market - are lack of time without any blocking. However, this is increasingly rare in recent years. There are services that offer unlocking capabilities to provide for a fee, but you can usually do it yourself for free, which is the perfect price.

You can get further details about to unlock phones by clicking the link below:

http://www.mobileunlockguide.com/

http://www.wikihow.com/Unlock-Your-Nokia-Cell-Phone