My home button on my iPhone 6s is not working?

It's more complicated than it sounds basically when I double click it works and brings up all the apps I've used but if I single click it doesn't work and it doesn't exit the app and I also can't bring up my control center or Notification Center and I tried assisted touch and that also does not work to click once it acts the same as the home button itself when I double click it, it works but not for a single click. And Notification Center and control center also don't work when I try to bring them up in assisted touch, does anyone know what's going on? And would it be better to take it into an Apple Store and get it fixed or to my cell service provider?

Take it to an apple store, since 6S is so new they will do it free. Assuming no water damage or anything like that.

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