You can try inserting an active SIM card from any other network into the iPhone. If it works fine, then the device is unlocked. If it doesn't work, then you need to unlock it. You can unlock an iPhone safer and easier using remote unlocking service. You can get the remote unlocking service for an iPhone from SuperUnlockCodes.com This method of unlocking an iPhone is safe, simple, affordable, quick and permanent. It doesn't require a jailbreak too. Good luck.