iphone 5 no sound
HI all, I have had my new iPhone 5 now since Friday, its all been ok but a couple of times now it loses the ability to make any souns, things like when click the top right button to switch it off it used to make a 'swoosh' sound, thats has stopped, also when I get an email the phone usually makes a sound, that has stopped....and finally when I usually get a call the phone obviously rings, that has also stopped a few times and it just vibrates.
I definately dont have the phoen muted in any way, the left hand switch on the side of the phone is not set to mute or anything, and when I switch the phone off and then on again sound is restored, any idea's, asume this is either a hardware or software issue, help !!!!!!
Thanks
iPhone, iOS 6