my volume down button wont work

Thanks for sharing.

Take the device to Apple for evaluation.

Try restarting your device. If that doesn't work, take it to an Apple store. If it is less than a year old and just stopped working, they will replace it for free (be sure to back it up to iTunes first). If you dropped it, you will have to pay because Apple will not replace a device due to "Human Error." If it is more than a year old, you will either have to pay to get it fixed, or have to pay to get it replaced.