Faulty cell phone

Bought a blackberry phone in December 2013 from the voda com shop in King William's Town Metlife Mall. From the second month the phone start giving problems and phone was send to Voda com East London for re pairs at no cost, phone was still under guarantee. Since that day the phone was send back another four times for the same problem. After the 5th day and still the same problem we ask for a new phone and receive a replay that the phone was beyond repairs and ********l ***** in phone. Met with Mohammed, Service manager at voda com shop and ask him to show me the ***** but said he will send the phone to Blackberry for reply. Receive feed back from Mohammed that we had to pay R855 - 00 for repairs. How can they re pair the phone now but the previous reply is that the phone is beyond re pairs. We dont want to pay the R855 - 00 because who say the phone will be fix.