dyeing and straightening

Hi. I have a BIG problem. My hair is dyed 2 colours, a little blonde chunk
in the front and the rest is, well I want it black. My problem is whenever I
dye it and use my straightener (which I use everyday because my hair is
so frizzy and nasty like that) that after a week the black dye is faded.
What can I do? Is it my straightener? I currently have a Duchi and also use
a Conair because of the smaller plates. PLEASE HELP!
PS what is a good brand of black hair dye that might help??

Well a better iron wouldn't hurt. Also after washing your hair put in Redken color extend total recharge. The stuff is amazing. Your color will not fade and your hair will look great. Also before flat ironing try Redken smooth down heat glide. It protects hair from damage, and color from fading.