Mine doesn’t charge for cancelled sessions even if last minute. None of the doctors/dentists/therapists ever charged me regardless how close to the appt time I cancelled.

Reasons were snow storm started, got stuck at work, car broke, got sick, family member got sick Etc not often but it happened, alwars fir legitimate reason (but how do they know?) they had no issue with cancellations, just rescheduled.

I’d not see therapists or doctors who charge for cancelled appts (unless of course there was my only option).