Inferior quality was refused to be exchanged

I bought a dress for my 4 year old daughter on the 30th January 2015. She worn for the first time on the 13th February 2015. The thin strap which was attached to the dress tore off. I took it back to earth child in sandton on the 14th of February and asked for an exchange. I was told that they couldn't exchange the dress as it looks like I ripped the dress. They took a picture and they said they will email it to head office and from the picture they will decide if I can get an exchange. While standing there, I was holding the dress strap in my hand and with a simple tug between my two fingers was able to tear the strap, again and again. The manager seeing this said I was pulling too hard on the strap and refused to give me an exchange. Earth child is made for kids, kids will play and be rough in their clothing but I never expected the dress straps to fall apart in my hands. Earth child quality is inferior and exchange policy is outrageous. I live 2 hours away from Sandton. It's difficult for me to come all this way for bad service. Now I don't have the dress or the refund. This would never happen at woolworths