Most campers have two locks on each door, a dead-bolt, and a regular lock. The regular lock is a type that most RV dealers (and some campgrounds) have a master key for. The dead bolt lock is the one the owner makes sure to lock if no one is to get in. Maybe, the dealer only locked the regular door lock, and a master key will get it open. Then you will have access to change the locks.
2014 Elevation 3616 5er
2015 F350 6.7L Diesel 4X4 - long bed, dually