Mobile cellphone

I brought a new cellphone 6 days later I went back to foshini as the phone batterie only last me 2hours,phone freezing everytime 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 the charge same foschini refuse to change the phone but proposed to send it back to repair. TC said you can return a phone after 7 days for exchange or refund.