How does 7 days return policy at pep work?

I bought a phone at pep store yesterday 28/02/2020 for R800 an then today 29/02/2020 I saw a Nokia c100 for R1000 at pep.i went to the store I bought the phone for an exchange but they refusing saying they don't do returns unless the phone is faulty. I really don't like the phone I bought can somebody help here please