Unhappy Nokia client

‎Dear Nokia

I've bought a a nokia 3 phone from jet sandton suddenly the phone just stopped working.i returned the phone back to the store. Seven days later i received an sms saying my phone has been assesed and quotation of R685.95 incl.vat.So what i need to understand is your return policy,the warranty period etc. The phone is only four months old and it had a heating problem before it went dead and never charge. Why do i have to pay for repair if is not physically damaged? Please help me on this issue i fail to understand I've spent R2199 for a working phone tha t was suppose to last me as much as it can but now the phone only lasted 4 months.It seems like your phone had a factory fault from the go since I'm not a technician i did not pick that up but picked up that the heating is abnormal. Now that the phone has died on me and has a gurantee of twelve months why do i have to pay for factory fault?How do you guys check your factory fault units,do your units passed QC ? Can someone check this as i need to know what other steps to take,please help on the issue above.