Unfair returns policy

Hi My Name is Debbie Mkhabela from Richards Bay. I sent my sister to buy me a phone and she bought the wrong phone from PEP( ***). Not even hours later I asked her to return it cos it was not the phone I had wanted. I phoned the store for a refund or to change it for the phone I had wanted and the gentleman (Smiso) told me I cant if it has no damage or faults. What must I do with a phone I don't want?