hisense t5 Phone

I brought a new cellphone 6 days later I went back to foshini Greenstone as the phone batteries only last me 2 hours,phone freezing every time i open a new application with message closing App . I went back to foshini explain the problem The test the phone the battery was very hot after just 20 minute of charging but foschini refuse to change the phone but proposed to send it back for repair. how can you sell faulty item and refuse to exchange after 6 day as your term and condition said .