Charging for late cancellations/missed appointments

Hi Everyone, I havent been on in quite some time. Just so busy.
Does anyone charge people for canceling at the last minute or close to their appt time or if they no show?
If so what is your policy.
I started implementing a $20 fee for canceling with less then a days notice because I have MANY young girls that will cancel 2 hours before their appt and a few of them have given me major crap for it and said some nasty things.

Also..I have 3 girls that are all friends and each of them tell me how the other is saying this that and the third about me behind my back. Saying I said stuff about the other one it is never true or the distort what I really said. I feel like I want to fire ALL of them as customers. It made me so mad that I said something to one of them and am sure she is going to tell the other two. What to do???