Iphone 5s sound problem

Hey guys,

I recently (being tonight) finished work and got picked up by my parents. When I got home my phone had sound and everything was working fine, but when I sat down on my computer and asked siri to make an appointment in my calendar, I noticed there was no sound. I tried turning it on and off silent and volume up etc. Still nothing worked. It works fine with headphones plugged in but not without. I've done normal on off, hard restart, plugged headphones in and out many times, cleaned the headphone jack, pressed on the bottom right of the screen but still nothing works. I've not dropped it once. How should I go about fixing this? I only got the phone for christmas so it's less then a month old as well.

Iphone 5s 64gb Black, IOS 7.0.4

Regards, Josh