4th repair to a Sony M5 since 14/12/2015

i have had ordered a Sony m5 in December 2015, since then the phone has gone in 4 times for repairs, i have barely used the phone to which i am subject to pay a subscription to FNB every month. i get no response from the manager when i mail her that is Shavintha Maharaj, just mild customer tactics are used. i cannot be paying for a phone that i dont use after i advised FNB on numerous mails that the Sony M5 has been recalled. the phone shuts off and cannot come back on until it is plugged to a charge point which is a hazard, the mother board burns out. how much more money and time must i spend in regard to this. after 4 times i have no phone. i really demand a response and a replacement coz this is not ethical from SOny, Triple S cellular, and FNB