When you place an order with us there is a pending charge implemented to the card. We don't capture the full transaction until your order is picked up or shipped out. When you cancel your order prior to picking up (or us shipping it out), the funds are immediately released on our end. It is then up to your bank to release the hold and make the funds available in your account.
For some banks this process is immediate, however it is possible for this process to take between 48 and 72 hours. If you still see a pending transaction and want to expedite the process, you can call your bank and let them know that the transaction has been voided.