HOW CAN I HAVE SMOOTH AN SOFT LOOKING HAIR?

So I just a haircut 3 days ago and it looks so straight soft and manageable and even if I showered it it still looks soft.(my hair is naturally straight but I had it rebonded or relaxed) and now is the 3rd day and its looks so frizzy. I always flat iron my hair because if I dont it'll look more frizzy but the problem is when i flat iron it it looks so dull and not soft! and it has some fly aways. What can I do? ANy techniques to make it look soft even if I flat iron it? :( I dont want to buy anything anymore.