Poor clothing quality

I bought a baby swimming costume at the Canal Walk store last month, on the 26 December to be exact. My daughter only wore it once and when I wanted to put it on again, the zip broke. I no longer have the slip and therefore asked your customer service whether I could have it exchanged and they said no. I must say that I am disappointed as I wasted my money on something that didn't even last three months and wasn't even worn twice!