Solution for App Start-up

Dear friends,

Hope you are all safe and doing well in this hard time!
The thing is that, I am planning to make an app where users can find "people who are giving service X", and use their services.
But the problem is that, I can't figure out how to make the service providers, pay particular percentage from the services they provide. Why I can't figure it out?
1. The place I am going to do it - people still prefer cash payment much more than cashless payments
2. If I am going to show contact info of service providers, at the time when user contacts them, they can bypass the system
3. Even if the app is going to work with request system - meaning they will request for service and an app is going to provide 1 service provider, how I can keep control of work done or not and also they payment?

4. I also though about the system like AirBnB has, since they don't let users to send phone numbers in chat, but still, they can send it by writing phone numbers in text format

You see the whole problem is that people still tend to do cash payments, which means that they will bypass online payment either way - thats my opinion.
I would be really happy and appreciative if you could help me with this issue.

Any ideas will be appreciated!
Looking forward to hearing from you.

#stayhome and #staysafe
Sincerely