Purple Ghd styler??did i make the right choice?

My hairs wavy/curly natuarlly and never stays but i my old hairdresser would use a ghd and would stay straight for days until i washed it. I think she used a styler but im not too sure. what ive noticed is that the purple ghd doesnt have a Temperature Settings on where you can change how hot you choose it to be just a on/off on. Is that normal? How hot does the ghd go? Did i make the right choice.