I purchased a Lumia 900 a few months ago for my daughter. It has worked fine up until now. The volume up button has stopped working. The volume down button seems to work ok, but I can no longer get any sound. I bought the phone on eBay, so there is no warranty. Is there something anyone could suggest to fix this problem? Is there a setting somewhere in the phone that would allow the sound to be turned up without regard to the buttons? Thanks for any help you could provide.