How to re-enable phone

If it was running iOS 7 and has been disabled or locked, it can only be unlocked through the original Apple IDs iCloud account... Unless it has been locked by the carrier (which is different to the software lock mentioned)... then you cannot unlock it without going to the carrier. they usually lock a phone if its been listed as stolen or missing. the only option would be to unlock it with jailbreaking software as a workable solution, because it will be the devices IPN settings that are blocked.