No flat iron works on my hair?

I have tried the Revlon hair flat iron, which didn't work at all. The wet to straight, which worked better but didn't really do the job. And now I have the Chi, which works a whole lot better, but my hair a couple minutes later sort of flips outwards. I have layers, and my hair is wavy, thick, and frizzy. I use Tresemme heat tamer. And also use the Garnier Fructis sleek and shine. I'm at lost when it comes to my hair. Please help!