Faulty tablet

I bought a mobicell tablet from Pep store in rosettenville on the 29 of December and on the 18 of January found out that the tablet was dead and not charging.I wen back the shop to lodge a complaint and the manage said I must wait for 3 weeks so that they will send the tablet to MTN.When I went back after the 3 weeks elapsed the manager told me that they havent sent my tablet.I asked for the tablet replacement since I have patiently waited for the 3 weeks that I was told to wait, but the manager refused my request, yet the tablet has a 12 month warranty on it.