It recently struck to me the method of booking appointments offline through WhatsApp, Phone call etc. is painful. The solution to this pain is provide an app for my client's customers to book appointments. How do I convince to the client the existing method is painful and can drive customers away?
You shouldn't have to convince your clients that they have a problem. Instead, I'd recommend starting with some user interviews to see if your prospective clients are experiencing the same challenge. A few questions you could ask, for example:
In the future once you launch an MVP, you can leverage product data & customer testimonials to strengthen your marketing copy and sales pitches (e.g., "Our customers increased booking by X% and saved Y hours.").
Good luck!
How to convince is not the right question.
Is what you’re describing really a pain point? Are there not already solutions around? What does your app adds to the already existing solutions?
My personal experience:
How would said app be easier than booking appointments through WhatsApp or phone calls? I imagine that this is what your prospective clients want to know.
Have you already had conversations and there was clear push-back or lack of interest?
I'm curious to hear more about your target customer.