I have iPhone but it is locked.how can i unlock my iPhone?

I have iPhone but it is locked. How can i unlock my iPhone?

You can unlock an iPhone using remote unlocking service. You can get the remote unlocking service for an iPhone from http://www.classicunlocking.com/apple/rs5wp8/ This method of unlocking an iPhone is safe, simple, affordable, quick and permanent. It doesn't require a jailbreak too.

Comes from my experience that iPhone can be locked for many reasons. Basically Unlocking is removal of SIM. You can use Tony's link to unlock the iPhone. I'm giving you another link http://www.themobilesmartgrid.com
You can use this.