Repear of Mobile Phone

From December 2014 I cant use my phone because their is a noice that the people cant here me.The phone switch of about 4 times when I speak to somebody.Mario the contack persone in the store send the phone for repear and the repear centre said it was the battery.Mario test the phone and the same problem appairs.From 5 January 2015 that he send the phone for repair again nothing is done till now.If you can contack Mario at Bela- Bela Mtn store he will tell you what happen with my contrack phone till now.Please Helo Peter can you help me.