WhatsApp is how Malaysian customers reply. The problem is using a personal chat list as the company operating system. Keep WhatsApp for messages; keep jobs in software.
Write three messages once
Confirmation after booking, reminder the day before, and on-the-way before arrival. Most no-shows are a missing reminder, not a bad customer.
Trigger from the job, not from memory
If the appointment is not in the calendar, the reminder will be late or sent to the wrong person. CleanMoo attaches communications to the operational record.
Do not run assignment inside the chat
Chats are for the customer. Assignment belongs on the job so the next admin can see it.