1998 Mercury Sable constant chirping in back passenger tire

In April this year I had brakes put on all around and also new rear brake calipers and rear brake rotors. The problem ... there is a constant chirping in the back passenger tire when I'm driving down the road .... when I apply the brake slightly it stops. I went back and had the person who did the work check it. I was told it wasn't the brakes but my tire??? Your input would be appreciated... what to do with the chirping bird in my tire?!!!! how to fix if possible thank you