I'm building a freemium SaaS product that instantly lets PMs identify and contact their users in-app to conduct user interviews. We're currently about a month away from a functional MVP that I would feel comfortable that customers would be happy with / see value from.

Everyone I've talked to says to pre-sell the software to 5-10 customers to ensure there is really demand for our product. I've never sold anything in my life, so wanted to ask whether anyone has any advice for selling a product that is a few weeks away for being real? What would you say in emails to potential customers, and if you get them on the phone, how do you ask them to put down a credit card number for something that they're not sure will actually exist?

What we've tried:

1. Cold email campaigns to our website

2. Creating a sales pitch deck to walk through with people on the phone: https://docs.google.com/presentation/d/1S_3q78ZR3FY8D1L6Dmv6X7yiZXgfD8rIJsbHDE6buvU/edit?usp=sharing

3. Creating a demo in one of our other products to show potential customers how we personally use the product

I'm not sure where to go from here, so any advice is appreciated!