Name of adult comedy movie

I saw the movie along with American pie 1 2 3 series . In that a teenage guy get a mobile phone and whatever he tel to others using it they will have to do/ For eg when he call her GF her mother take call and he tell something and she does and in other scene he get in accidentally when his brothers GF is bathing and he say " assume i am not here : and she goes on bath and drying