If your hair is still greasy after you wash it and no matter how much you wash your hair the hair is still greasy you likely have a condition known as Seborrheic dermatitis that affects your hair and scalp and makes your hair overly greasy or oily.
You may also just have an overproduction of oil in your hair and may need to use a different shampoo for oily and greasy hair.
When washing your hair you might also be irritating your scalp which can overstimulate your glands and cause them to make more sebum that causes your hair to remain greasy after you wash it.
Another thing is that you may not have washed out all the shampoo or hair conditioner and have leftover shampoo or conditioner.
So try washing your hair out again.
You might also try washing your hair using some apple cider vinegar which can sometimes help get the grease and oil out of your hair.