The $50 charge listed when a Levy rental scooter is unlocked is a temporary hold that is placed on the card until the scooter is returned. The charge is cancelled the same day the scooter is returned but often appears as a charge for several days after it is cancelled. It can take 1-4 business days for your bank to erase the line item after it has been cancelled by Levy. If you have returned your scooter and still see a $50 charge you would need to contact your bank.
Reserving a scooter will also trigger a $50 hold similar to unlocking the scooter. In this case, the $50 hold is released when the reservation is cancelled or the trip is begun.