cheating by providing defects goods

I bought a mobily broadband on 27/06/2011. it does not work from that day.I informed the shop ,they didnot respond properly and said to contact costomer service center. I give the details below:
name of shope  ---------SMART MALL,ARAR
MODEM NO -----------049254
SERIAL NO ---------  S/N.. SAM 1229C6100WN-049264
COST --------------350 SR