It’s easy to take away the battery cover. There is a hidden screw under the warranty label. Take away the battery after the phone powered off. Loose the lower half of the back frame with a spudger. Pry up the upper half of the back frame carefully. Remove the back frame. There is some sticky at the edge of metal sheild. Pry off the flex cable. Install a new button flex cabel. Make the flex cable stick to the back frame at the right place. Fasten the back frame. Install the battery. Power on the phone and then adjust volume. Fasten the battery cover.