My hair changed during and right after high school, I guess it was puberty and hormonal changes that did it.
I was told by my hair stylist that the type/brand of shampoo or conditioner you use does not really matter. I usually buy whatever is on sale and she said that was OK.
I now also use an anti-frizz smoothing creme (again whatever is on sale). I use about a teaspoon and work through my ends and the really wavy parts but not close to my scalp because my hair is so oily.
Then I blow dry and it's smooth and silky. If I just let it air dry with no product it is very wavy and frizzy. I usually let it air dry through.