Online booking system problem

If a parent goes into the parent portal on a Friday afternoon and books for the Friday morning class (obviously to start next week), they are incorrectly charged for the Friday morning class to start day, when the class has already taken place! Not to start the week after (as it should be).

We have never come across any online booking system for any activity that charges you for a class that has already been! This should not programmed on a day to day basis but on a minute by minute basis, where a class that has already taken place is not charged for!!!