Refuses to exchange broken item

My son and his grlfriend bought his brother a 2 Pack of headphones for christmas. These were broken 2 months later. He's been asking me for about 3 weeks now to take him but I havent had the time. The slip is nowhere to be found. They asked for some proof as they can trace the slip, so I was very impressed. Phoned her and she sent a copy of Bank sms, States clearly Musica Mall at Reds and the price. After all the time wasted getting the sms, waiting for them to trace the slip I was told they can only go back to 28 Dec.!!!! Now they wont exchange it without a slip. They agree that was the price with 55c for the packet but sorry. We sell you **** for R250 which lasts for 2 months and you take the loss. We've *****ed you and we score!!! So sick and tired of SA's SHOCKING CUSTOMER SERVICE, SHOCKING QUALITY of products sold and dont give a damn about your loss. We had the packaging but not enough proof that the item was ACTUALLY PAID FOR and not ******. Actually an insult to me after spending nearly R2000 there myself in December. Never again, they wont see my money again!!!!