The art of the "cold pitch" is definitely something that needs to be worked on, and doesn't come naturally to everyone.
A couple of quick tips:
1. 4 is not a big enough target group, you've got to cast a bigger net. Try pitching 20, and aim to get 3-5 responses.
2. When sending a cold email, really think about what you are offering them. Whilst you'll get the odd good egg that simply wants to help - you can't expect entrepreneurs and small biz owners to take time out of their day to answer your questions. To counter, why not tell them you're conducting research in the space, and would be happy to send the finds/reports back to them in a nice format, which could in turn help their business.
3. Don't give up, keep hustling. Try changing around the emails slightly, track which emails convert into responses, and fine tune from there.
Good luck and feel free to book a call if you want to chat more.