Weird Hair Problem help?

Okay, I'm Asian and have really straight hair and whenever i try to curl it with a curling iron or a flat iron my hair gets straight again after about 3-4 hours , but it doesn't get really straight just some waves left or little curls (if i curl it) and if i put hairspray on it'll just slip right off like no kidding... And whenever i try to tease my hair for volume and put hairspray on it 3-4 hours the hairspray gets less harden and the tangle will untangled and my hair would be flat again. I really don't like my hair, but most of my friends envy it and i can't understand why. If any of you guys can give me some advice like for the best hairspray that can hold my hair really good that will be great. If some of you guys have the same problem with straight hair please tell me what you guys do with it. Thanks :)