Then don't accept the auto-correct spelling. When you see the auto-correct change, if it is not what you want, then don't accept it. You have control over that. If you are seeing the 3 suggestions above the keyboard, then the way you typed the word is the first one of the list of three. Just tap on that one if you see the center one turn blue like it is going to be accepted. After "learning" your spelling with using it a few times, it will not attempt to change it.