We understand the flexibility an unlocked device gives you, andreslic. Deloused posted a great resource, which is a link to our unlock policy. We do not lock our 4G LTE devices and no code is needed to use them with another carrier.
The device may be blacklisted if it's tied to an account with an unpaid balance or sometimes devices have been incorrectly reported as lost or stolen.
What are you trying to do with the iPhone 5S? Where are you running into trouble with the device?
Follow us on TWITTER @VZWSupport
If my response answered your question please click the _Correct Answer_ button under my response. This ensures others can benefit from our conversation. Thanks in advance for your help with this!!