He refused to Understand my situation and help

I got a post box bought at Builders Warehouse as a house warming gift from my acquaintance's's parents for my study materials that I will be receiving as door to door post. unfortunately the place in which I live they said that I am not allowed to mount up this post box and so I had to return it. I don't have the slip and the people that bought this gift for me are in Cape Town now, it is still unopened and the bar-code is still on it. I called Builders warehouse on Thursday morning and spoke to a guy called Van Roy, I explained my situation to him and he said I can come return the post box. how ever when I got there, the manager took my situation so lightly as he refused to understand and help me. He even laughed it off as i was explaining. No I have an unopened post box that I do not know what to do with and the Manager Alex refuses to help me. It was a holiday and I had to waste my money and time going to the shop with falls information that I would receive help. I am deeply saddened by the way this matter was handled and the comment's passed by this guy. what does he expect me to do with this post box now...?