Damaged phone within 7 days

On 09 June I bought a phone by PepCell, following day the screen cuts and has ink marks on it, I think it will pass and it does. Friday again it does this again. Saturday I go to the store the lady tells me she can't return the phone because she didn't physically see the problem, basically telling me I was lying. I let that slide, then Sunday it does it again and I take pictures of it on my other phone then today, around 5pm, I take the pictures to show the consultants. I spoke to Yandi, she imp**** that the pictures were a lie and I was lying about the phone hence she needed to see the phone doing the ink thing with her own eyes too. Again, I take the insult and tell her as soon as the phone does it again I will bring it on condition that I will get a new phone as per the 7 days guarantee and she says no because the 7 days will have passed. I immediately call the customer care line but there was no answer. I left the phone on the counter and told Yandi I was not going to take home a phone I know has a problem and she said she would leave it there and another customer will take it, I told her I don't care. I won't be called a ****! I want my money back! I will not stand for insults