Practitioner booking on calendar

I have just joined this forum and I am trialling Cliniko.
We run a health centre with four therapy rooms and a hall, using a ‘manual’ system. Therapists can make bookings for a choice of rooms, either weekly ongoing or ad-hoc. A receptionist has the role of taking therapist bookings and client appointments. These are recorded on top of each other in one calendar per room.
In Cliniko, we have created a calendar for each room as a ‘business location’. Entering client appointments is straightforward. The nearest approximation we can get to therapist room bookings is their ‘availability’. Cliniko allows more than one practitioner to be available at the same ‘business location’. For us, that means a room can be double-booked. We see no means of safeguarding against this.
Therapists can log-in and change their availability, but we see that they can also change the availability of other therapists. We see no means of safeguarding against this either.
Can anyone advise on how we can overcome these two issues?