Pee on an electric fence. That's free, and it should take care of the hair problem.
Seriously though why do girls with straight hair want curly hair, and the girls with curly hair want it straight. Save your time and money and celebrate what God gave you. You might be surprised at the people that would prefer you the way you are.
You can make your hair stay straight, you need to wash your hair, condition it and then towel dry it. Then, put straightening product in your hair and then gently blow-dry your hair on the lowest heat setting. After that, work in more straightening serum as you dry and then finish with a hair straightener. If that doesn't work, you can consider rebonding. For more information, visit http://www.ehow.com/how_4885352_make-hair-stay-straight-day.html.