Hey! If I got it right then you probably need 2 apps:
for the clients (see available services, chat with you or the secretary for guidance, book an appointment, set an alarm or reminder, see the address and go to Google Maps for directions if needed, receive notifications if the time has changed by the service provider, etc).
for the service provider (set the type of service, available times, chat with clients, etc).
This app needs online updating and accounts for both clients and your business which will be implemented using Firebase which is fast and secure, also besides writing your business' location, it can be chosen on Google maps using Google Map API for clients' convenience and better service.
Also, I guarantee 6 months of full support with the application in case anything goes wrong and more support even after that, anytime you need it.
I've had some E-commerce projects like this one before and have some good experience with them. I'd be glad to help you with this project. If your interested please don't hesitate to contact me.
Sincerely