Hey Danielle,
First, make sure that the ring/silent toggle on the top of the left edge of the phone is flipped to ring (not displaying a red dot). Then, go into your settings and click on Sounds. Under the "Ringer and Alerts" option, make sure that the "Change with Buttons" option is toggled to on. Try using the volume buttons again.
If this doesn't fix the problem, use the slider under the "Ringer and Alerts" to turn the volume all the way up. See if this allows it to make noises.
* If the buttons work after toggling the "Change with Buttons" option to on, your device is fixed!
* If the buttons still don't work but the screen's slider allows you to turn the volume up, you will probably need to [guide|4337|replace the volume control cable].
* If after all of this, you still do not hear the ringer or alerts, let us know and we can troubleshoot further.
Hope this helps! Good luck!