Nokia 5310 problem

i have a problem with my 3 day nokia 5310. after i gave it to my friend to see it, the buttons for the volume stopped working. they work but when it gets to increase or decrease volume...nothing happens. can you tell me how to fix this problem? or from where to set up the buttons. thank you in advance.

better you take your phone to the Nokia Care Canter, I never have like it before.