When any service is sold out or not available the day they are looking for it tells the guest "No time available try another day". That is making it sound like the entire day is sold out when it is just one service in their order. Or there may be something very similar that is available. By just saying "Choose another day" that person may just jump to the next place.

There should be a call to action for the guest i.e. "One of your services may be unavailable please contact ###-###-#### to speak with a reservationist". At least this way you are not leaving the person out there to possibly just move on to a different competitor.