Flat hair? help please?

I have extremely flat hair. I was born in Bangladesh so i guess you can say i have asian hair. My hair's texture is really soft and everyone loves the feeling of it but i hate that its so flat and straight. I never in my life used a straighter on my hair cuz my hair is already so straight.. i come out the shower and its straight. I tried using John Frieda voluminous shampoo and the moose but it doesnt work on my hair.. its still flat. I tried blowing it upside down after taking a shower but it still doesnt have volume in it. Teasing my hair takes time and i hate the tangles. Is there anything else i can do to make my hair have more volume? Thanks.