If you have a mirage plus, the hub slides in and out. Why would you need a prop shop to install a hub?

The whole story was I needed a bigger prop so I went to my local prop shop and bought a used reman prop to save a couple bucks. It had the solid hub in it, I spun it, they put the new hub kit in, I spun it, now they are puttingnin a stronger hub kit from mercury in it. Something is supposed to be longer or something. Either way they are fixing it because I bought the prop from them. Why should I have to donit when I never got to really "use" it because it blows as soonnasni try tonget on plane