Bad service,

Sent my sister to purchase decoder at pep came back with the wrong one which is openview, went back to the store it was closed already. So today went there with original package and slip and they tell me they don't do exchange and I asked where's the policy that states that even on the till slip on in the box is stating that they don't do exchange on decoders... I'm really frustrated as I don't know what am I suppose to do with decoder that I don't need. If I have to take this further I will because I telling they were suppose to inform their clients of such