It is a good idea. you may want to better understand why customers may contact a business and make the messaging experience much smoother for instance by having sample text message ready to be used by users.
It is interesting to see how a community hardly using computers for reservations uses an app. I wonder if convincing barber shops or other similar businesses to use the app is difficult.
The 20-80 rule is great to manage the existing situation. I believe ever so often we should look up and see what's ahead of us and adapt which requires to go beyond what existing customers are asking.