Cellphone

My grandmother bought my 10yrs old cousin a cellphone at Pep store Jabulani Mall which my cousin only used for 3 weeks or so and it stopped working. My gran took it back to Pep and was told to come back for it after 7 days which she did and the phone work again for about 2weeks and again it stopped working and she took it back to Pep and was advice to take it to Vodacom repair centre (Jabulani) which has been about 2 months now and she has been sent from pillar to post even after it has been confirmed that the phone stopped working due to factory fault and they are suppose to replace the phone. My gran was given a phone yesterday and she found that it was also not working. Please help.