Bad customer service

I bought pampers from another branch at pick n pay and so I decided to return them on the nearest pick n pay for an exchange the mananger from pick n pay Vosloorus xolile told me that I can't exchange them. And I bought them on the 29of November so it's the 11th of december I dnt understand the pick n pay policy Becouse I had my slip and the nappies where not opened. I just needed to exchange for a bigger size, I'm so disappointed with the service I got frm pick n pay in Vosloorus