Mr. Price quality only last for 30 days

I bought a bag from Mr. Price waterfront in cape town. The zip of the bag broke in less than 30 days, I went back to the store 7 days after 30 days of their return policy and the manager Malusi said he will not accept my return. The problem i have is, that do Mr. Price sell goods that only last for 30 days, not even 6 months. That means I have to buy goods from them knowing that it will not last me for 6 months at least which is poor for production. All I want is an exchange for another bag. I will never shopping at Mr. Price again. I would rather go buy at a informal shop along the street that I know is a poor quality like Mr. Price that might last me for 30 days.