How to flatten frizz/flyaways in hair?

I have medium thick hair. It's wavy, brown, and about half way down my back. I always get a lot of flyways in my hair, at the roots mostly. Also my hair gets frizzy. Not too frizzy, just where my hair line is I get a bunch of frizzy fly away curls and waves. I know I can't get rid of them, but how can I like flatten them. Like make themeless noticible. No heat please! Thank! :). Oh and also, I only use cold water on my hair, in the showwer, some days I use just shampoo, sometimes just conditioner, sometimes both, and sometimes none cause it's bad to wash hair too much. Or so I've heard. When I use conditioner I let it sit for lik 5 min. That makes it soft, but I need to flatten frizz and flyaways!!! Thanks! -ERA