Last September, I finally upgraded from my ancient Blackberry to an iPhone 5. I still miss typing on keyboard buttons, but other than that, the phone has been great.
Then more recently, the Volume Down button on the side of the phone stopped working. Volume Up was just fine, but I could not lower the volume on the phone unless I clicked on iTunes, went to a song, and slid the volume control manually.
I did a quick search on the Apple support forums, and found that this is a common issue with the iPhone 5. So, since my phone was still under warranty, I made an appointment with the Apple Genius Bar to have the phone checked out.
The tech took a look, and within a few seconds, he said, "Okay, it's a physical problem with the button, so we're giving you a new phone." I had already backed up everything on my computer the night before, so after erasing everything on the old phone, he handed me a brand new iPhone 5, just like that.
If you're experiencing the same issue, get to an Apple store while you're still under warranty. Just make sure you back up all of your data and pictures first!
**UPDATE**: Just wanted to mention that if you are purchasing electronics, it's always best to use an American Express card whenever possible. They have an "extended warranty" program that was a godsend for us when my daughter's iPhone 5 cracked and wasn't working properly. Her 1-year warranty had already expired, but we contacted AmEx and they paid for her to get a replacement phone from Apple. Something to keep in mind!