How do you reprogram a Mercedes Vito key fob?

To reprogram a Mercedes Vito key fob, first, ensure that all doors are closed and the vehicle is in the "off" position. Insert the key into the ignition and turn it to the "on" position without starting the engine. Press and hold the unlock button on the key fob for approximately 5 seconds, then release it and press the lock button once. Turn the ignition back to the "off" position, and your key fob should be successfully reprogrammed. If this does not work, consult your vehicle's manual or a professional locksmith for assistance.