Not having the use of your volume buttons can cause some headache. Some of the functions that it can make difficult are: listening to music, conversation volume, and ringtone volume. It's usually not the button itself that is bad, more than likely it's the flex cable connecting the buttons to the motherboard. This flex cable also supports other functions in your iPhone such as the headphone jack and the ring/vibrate switch. If you leave this malfunction untreated, you can expect to lose functionality in these other areas as well.
We always have the parts on hand to fix this malfunction right away, so when your phone arrives it gets fixed and shipped back within 24 hours.