SinglePass Curl Ceramic Long Barrel Curling Iron - Graphite : Doesn't work on my hair

I've had this curling iron for nearly 8 months. In that time, I have tried so many different techniques and products in an attempt to get this to work for my hair. Sadly, it just doesn't. I have naturally wavy hair and have never had any problems with any other hot tool holding styling in my hair. It takes me 10 minutes to curl my full head of hair and by the time I get to the last curl the first curl has already completely fallen out. Within an hour my hair is pin straight. I don't know why this doesn't work for my hair at all, but I have finally given up on it - even extreme hold hairspray can't keep my curls intact. I'm so disappointed because I had high hopes for this curling iron.