I don't mind when a lady has to cancel and they let you know. Shit happens, I can understand.
What I do mind is when they ghost you. You confirm an hour or whatever before the appointment as requested and then you don't hear anything back. No reply to say they have to cancel or reschedule, just completely ignore you.
Twice this has happened to me in the past week. Second lady in particular has almost 200 glowing positive reviews so I thought she'd be more professional. I already started driving to her place after I sent the confirmation text. 40 - 50 minutes later still heard nothing back so I just cut my losses and turned the car around