First, if you're thinking about buying an Apple device from an individual, perform the transaction at your carrier's store. Taking this extra step will ensure the device is activated and has no security issues. If you've already purchased a device from a third-party store, visit that store and have them exchange it. Trust us; it's easier to get a new one. If you purchased the device from an individual, it is entirely up to that individual to unlock it. Apple will not reset the original Apple ID, nor will they help you get the passcode.