No Contract Cancellation with Vodacom

I bought a cell phone Sony Xperia Z1 on contract on the 10/12/13 @ Vodacom Chatz Mall of the North they give me a cell phone that was not functioning properly ( it indicated system update & it flashes on the screen, it goes off every 10-30min without me switching it off ) I submitted my letter on the 24/12/13 appealing for contract cancellation, on the same day the store manager received the cellphone including everything it came with in its original box, but they never cancel my contract, since i was having an initial contract with vodacom i called vodacom customer care, they advised me to use Vodacom M65 deposit slip & my initial number as reference to indicate that i was paying for my initial contract, i did so but later on both my lines were closed or offline then i stopped paying because the store held the cellphone with them, even today. Vodacom blacklisted me for that, i then called vodacom customer care they referred me to their lawyers & the lawyers requested detailed explanation on an affidavit & some documents which i did send, when I'm calling them(lawyers) asking for feedback they say my case was send back to vodacom head office are the one to solve it. plz help,