All my clients need to confirm at an agreed time (usually when they are leaving to come to me) and if I don't get the confirmation I send a text telling them that their appointment is cancelled as I didn't receive confirmation.
The genuine ones get back asap. If I don't get a pretty much immediate response I just move on to the next booking.
I never send anything inflammatory as it's counterproductive and you never know who you are dealing with plus it's a waste of my energy. Unlike a lot of other ladies, I do block undersireables as my phone then doesn't receive calls or texts from them. Obviously, if they get a new sim or phone then I won't know anyway but I've never had anyone go that trouble.
Tbh, I tend to have a feeling when they book if they are going to be flaky so I will take a standby appointment (I ask the client if he would like to be on my reserve list).
If I'm in an area where I know or decide a lot are trying to waste my time then I throw my appointment system out the window and work on a first come first served basis.
That way, I am always in control and whilst I do get clients who don't confirm, I very, very rarely get a no show.
(I did have some cunt at Southend who confirmed, said he was leaving and then never turned up but thankfully that type behaviour is so rare, I thought it worth a mention
)