Iphone acting up
okay so I bought my IPhone 6 plus from T-mobile in the beginning of December 2014. my phone has worked perfectly fine until around March 17th 2016. out of no where it started to spas out.. opening apps on its own, calling people randomly, hitting buttons and typing and sending messages all on its own. I have tried resetting my phone a couple different times, I even tried completely wiping out my phone and making it like it was brand new and this problem continues. there are times that my phone works fine, and some times that the problem seems to have gotten worse.
could anyone help me with getting my phone to work again? if I take it to the Apple store would they be able to fix it???
iPhone 6 Plus, iOS 9.3.1, T-Moblie service