Appointment booking app - How do I convince my clients about the pain of booking appointments offline?

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:

• What is your greatest pain point when it comes to booking appointments with customers?
• How do you currently solve that pain point?
• Why haven't you incorporated a scheduling tool into your workflow?

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:

• I use Calendly for scheduling video calls. I love this product and it has a free tier. I pay 0$.
• I recently booked an appointment at a restaurant website via a widget, and it worked great.

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.