refuse to take back/exchange for my money

I bought a defective Adidas track pants from Tekkie Town and I belive it to be a knock off, when I took it back their head office in George refused to take it back claiming that I have torn it and if I am not happy I must take this up with Adidas which is not my supplier but theirs. I was dealing with Betsie Van Vuuren and Leanda Coetzee. what is funny about this the manager at the store was willing to exchange because he saw and touched the product and these other people they just looked at the picture sent by the store manager and decide to decline my claim