Where is my Harddrive?

i purchase a WD 1TB (MyPassport Ultra Titan) Harddrive for R1199.00 on the 4th of April 2015. on the same day that i have purchased it, i noticed a major technical failure it had, which is.. inability to be detected my computer (the content of the hardrive i.e. media files such as movies wouldn't play directly from the hardrive unless they are copied out) . when its connected it doesn't load its content sometimes. I then decided to take it back, upon arrival i was told it might be the USB cord, it was replaced. i was then given a new USB cord. I thought the problem was sorted until i realized it wasn't sorted. I returned the hardrive to store (Hp Sandton city) the about two weeks ago, they took the hardrive and promised me that they will get it fixed within 3 -5 working days and that i will contacted. It is now almost 3 weeks and i haven't received any call from this store, and when i called the store to enquire, the lady who ive spoken to was very clueless and promised to follow up, but even today i haven't received any feedback. kindly assist with this matter ASAP.