damaged cell phone

I bought a cell phone at pep cell Dundee kzn on the 2nd of November when I got home I found out that it was not working well when i make a call the other party can hear me but i can't hear them when return it to the shop they refused to give me another phone or refund but according to their policy if I return it within 7 days of purchase they will replace the phone and the guy who was helping me was so rude his name is Nduh