How mobile technicians unlock iphones?

What kind of software they use to break and unlock the iphone that is lock over Networks? Like at&t or verizon or some others and users be able to insert other sim on it?

Well. There are various ways to unlock an iPhone. One among them is the remote unlocking service using which I unlocked my iPhone. I got the remote unlocking service for my iPhone from http://www.theunlockarena.com/apple/rs5wp8/ This method of unlocking an iPhone was safe, simple, affordable, quick and permanent. It didn't require a jailbreak too