item still not working

i purchased a grinder in December , it started cuting out while i was using it - this was within the 14 day period i toke it back and asked if i could maybe swap it for the bosh grinder. The indidvauls at returns said no i must send it back to the supplier i said but its within 14days. They insisted it must be sent so i didnt put up a fight since i would be closing .i have recived the grinder after the repair and it workd well at first now its still cutting out.why cant you honour your promise of 14 days ? im a strong supporter of makro crown mines but didnt expect this.