Deployment of a chatbot for a client

I would like to have a feedback on the deployment of a chatbot I have developed with make and voiceflow.

Does it make sense to ask my customers to have a second phone number to connect to whatsapp business, so that I can deploy the chatbot there?
This seems like a limit because I would need to deal only with clients paying 20$ a month on average for a double number (?).

The chatbot is supposed to manage customer service and bookings.