Complaint against PNP Clothing The Reef Mall

Today I was at PNP clothing at The Reef mall in Germiston. I bought pants during December. I at that stage bought two of exactly the same ones as it then was on a cheaper price for two. I have only wore the one and have put the other one away until now. When I wanted to wear it for the first time this week, the zip was broken. I then went to Pnp Clothing at the Reef mall where I bought it to return it. I wanted a refund and not the other pants, as I do not want another one with the same quality. I was told it must have been returned within 30 days. I gave them the tags and the slip. I said to the lady I understand what she is saying, but then she must call head office so I can discuss it with them, as the circumstances was of such that I only had to wear it now for the first time since December. They refused to call head office to help me, they refused to help me, stood there and discussed me with each other, which I could not understand and refused to give me their names, in order for me to discuss amd try to resolve it with head office myself. I do not want the same pants again as I do not want to sit with the same problem of broken zips and then it has been worn. When I insisted that they must give me their names they refused and turned around and walked away and left me standing at the till. I then just had to leave. Can someone please assist me.