iPhone 6 mute button problem

Hello,

a few days after the end of the guaranty the mute function of my iPhone 6 is not working safely. In the position silent (red) the mute function turns on and of by itself when i carry the iPhone in my pants pocket. I recognize that a soft touch of the mute button switches the mute function on and of.

Does anyone knows a call back action from apple for this issue/bug?