Bought faulty item now I have run around to repair it

U bought a decoder a month ago since day 1 its giving me problems it works for days and one day it will just stop, u leave it just goes on by itself, explained ths to the store employee n jst because when he put it on it worked he tells me there is no problem have to take it for repairs at N1 really something not even 2 months old have to take it for repairs an disgusted forked out my money for something I have to take to repairs within 2months.