Changing staff availability after booking page has been published

We have a booking page that has been running for a while. Our departments use it to book a quality audit by the quality team. Due to changes in their availability we now want to change the days where the staff is available in a certain services. 

For instance: Person A was bookable on monday, wednesday and thursday and will now only be available on mondays. 

We tried changing the availability through the staff tab. We deleted the days that person A was no longer available and saved the page. However when checking again those changes did not last and the previous availability is still there. 

Are there other ways in which we need to change that availability or is this the way to go and is there an error that occurs on our end? 

The motivation for the changes also lies with a default setting from bookings in which Bookings always selects the first available user from the pool when checking alfabetically. Which causes Bookings to mostly end up with one user. We hope to counteract that behavior with the availability changes. Any other workarounds on how to do that are more than welcome!