My round button will not work

My round button will not work. I have been to the apple store three times. Each time, I'm told that it's a hardware issue, then the second person comes out and tells me to update the software. I did that and it is still doesn't work. I'm turning off everything, so the phone isn't overloaded. I was told by the last Apple person that he wouldn't "throw new phones away" on me because the person who checked me in said that I need a new phone (actually 2 apple guys have said that). What should I do? The phone won't work without that button and it is very frustrating. The button literally sticks 😟