How to Identify Bot Traffic(PPV, Native)

Hello,

I am working with different traffic source PPV, POP and native networks. I try with different angle but not getting success. By researching I found that Few Traffic sources are sending bot traffic. How to identify them?
I speak to them. They mentioned give us those IP's. what is best way to identify them?

Are they give refund on bot traffic?

Looking for help to identify bot traffic.

Thanks in advance