bad service from pep cell jabulani mall

i bought a cell phone at pepe cell jabulani mall i missed placed my slip after i purchased my phone only to find out the phone is faulty i cant press the buttons on the when i go back to the shop they tell me that they cant fix it without the slip while i used my card to swipe i still have the box they want an id when you purchase the phone why cant they take my id see the emei number i feel like they faulty goods they