Blackberry 9720 repair

I took out a cellphone contract in October 2013 and received a brand new Blackberry 9720. A few months later the phone constantly died even though it was charged, however the battery life became very short as well. I took the phone in to Tygervalley Vodashop and after it was sent for repairs, I received a new phone of the exact same model, since it was a manufacturer's problem. All good and well. <br> However, recently the new, replacement phone started to do the exact same thing - dying without reason and sometimes it takes hours before I can revive it. Of course I took the phone back again to the Vodashop for repairs. Only this time I was quoted R358.00 to have the phone fixed, because \the battery is only guaranteed for one year."I rejected the quote"