REFUND REQUEST ON A MOBICELL TABLET THAT HAS NEVER WORKED!!!!!

I purchased a Mobicell tablet for my son on the 27th Of October using my account at Greenstone, a nice and well-mannered guy (Trenton) assisted me. He advised that the tablet was locked on a Vodacom network of which the phone will only work on Vodacom network and I accepted. He inserted the simcard and everything was ok. The next day the phone didn’t have network, I thought maybe the simcard was damaged and inserted another Vodacom simcard but it still had no network. I took it back and again Trenton (always willing to assist) helped me book in the phone for repairs he advised that I will get an sms when the phone is ready. I waited for weeks with no word from the store I decided to go and check and only to be told that the phone was delivered a while back. Another lady assisted me as Trenton was not in and advised that the phone was flat and she didn’t have a charger, the phone was actually changed as it had a new IMEI number. Took the phone home, charged it but it still had no network. I took the tablet back on the 31st of December as I didn’t want it anymore as Mobicell Tablets proved to be ****, Trenton advised that he could not do a refund as the phone has a 12 month warranty. Again the tablet has been booked in for repairs for “repairs” and I have to wait for another month????? As an employee I understand that his hands are tied as he said he could not do a refund for the tablet. I am paying for something that I’m unable to use, I DO NOT WANT THAT STUPID TABLET ANYMORE AND I WANT A REFUND ON THE STUPID PHONE. R900 is a lot of money and surely I can get a better working tablet with actual signal.