my opinion

hello angelina,
 for me I would rather u tell me the truth.   let's face it,  providers do this for a living so I'd expect most ladies are usually busy most days of the week.    it doesn't bother me if you tell me that your booked.   considering how beautiful you are and from your  amazing reviews I'd expect you to be busy!!

and a simple unavailable  is the truth. You don't owe an explanation as to why. Could be another date, could be dinner with friends or family, or getting your hair done. The hobbyist doesn't need to know. If he insists for a reason its a little creepy. Its your time to schedule as you want not his.

I want her to be honest. She's running a business so there's always a chance that she'll already be booked at the time I want to see her. What I won't accept is a provider that double books and then lies to cancel a couple of hours before our session, which is what happened to me this past weekend.

You can tell me you're unavailable for any reason or no reason at all, I'm a curious sort, so I'm interested, but I don't need or expect one.  I dislike discovering I've been lied to, big turnoff.

If you don't provide a reason it's never a negative I just assume you have personal stuff going on, which isn't really any of my business.  

If you do give a reason, be honest, it's amusing how many times they forget what reason they gave when it comes up in idle conversation.  Be aware if you do provide a reason I sometimes feel it's fair game to discuss when I meet you, so if you tell me you have a kids rehearsal I might ask you how it went.  I'll take a hint if you divert the topic, just don't be surprised.

tldr; Unavailable or reason, never booked.  If reason be honest.

I prefer a provider to tell me she isn't around because she is at the finals of the mechanical Bull Riding competition.