DEDUCTING EXTRA FROM MY BANK ACCOUNT FOR TRIP!!!!

Booked a trip which came to R89 as per the app charge. Lo and behold when the trip ended my bank account is credited with R89 and another R33 is deducted from my account!? Surely this is bad business practice to just deduct an amount from my account that I didn't give my permission for? I'm not pleased with this at all!!!!