Why is answering mid-appointment the worst option?
Because it costs you the client you already have. Someone paying for your attention notices when they lose it, and the caller gets a rushed conversation from someone who cannot check a calendar with one hand. You take a small revenue risk and a large reputation one at the same time.
Solo operators feel this hardest. With a team, someone else picks up. Alone, every call is a choice between two clients, and you make that choice fifteen times a day.
Does batching callbacks work?
Partly, and it is the cheapest thing to try. Set two windows a day, tell people when they will hear back, and stop feeling guilty in between. It works for existing clients who will wait.
It works less well for new enquiries. Someone comparing three salons will book the one that answers first, and by your afternoon callback window that decision is usually made.
Why does moving enquiries to WhatsApp help?
Because messaging changes what a delay means. An unanswered call is a rejection; an unanswered message is normal, and the thread survives until you get to it. Clients already understand this, which is why so many of them message rather than ring.
It also gives you something a phone call never does: a written record of what was agreed, and the ability to answer three enquiries in the two minutes between clients rather than one.
What if the reply still has to be you?
Then you have moved the problem rather than solved it. The step that actually removes the work is something that answers the repeated questions and books the appointment without you, and hands over the ones that genuinely need you.
The test of whether that is working is not how clever the replies are. It is whether you finish a full appointment without checking your phone once.