Poor customer service and rudeness

When u buy something it's written on the slip that you should return within 7 days...I bought something on the 5th returning it on the 12th and I'm told 7 days ended on the 11th. What the hell is that?can they not count?5+7 equals 11 and they will not give my money back.Worst of all when I call their customer care this girl has an audacity to drop the phone while I'm still talking.This is not on. I WANT MY MONEY!!!