How to unlock iphone 4 by sprint?

I found a iPhone 4 by sprint and it has an password on it cause you tell me how to unlock it please?

Yes, you can go on Ebay and purchase special made sim trays such as Gevey and others. Most of them are around $20 but there's a downfall to them. Just email me at Brian112123@gmail.com for more information.

First thing you need to do is to look for your iPhone's IMEI number. If the contract ends, you can contact the carrier by phone, via the web or in person. When you will be lucky enough and they emailed or respond back with a positive reply, back up and restore your iPhone in iTunes. If not, then You can ask for help on iPhone unlocking enthusiasts.