How can I make appointment for change my old I phone 4s new one

My phone is contract I buy from apple store.its one years ,my phone sometime is not working but, I still pay my contract Its hearing problem and sometime stop by self can't work lots of problem so I want to change my phone and I want to gate another phone by exchange so tell me what shall I do now last time I went yours hope their told me I have to make appointment by online .so please kindly let me know something .