iPhone with TFG they're very frustrating

I took iPhone 12 pre-owned from Markham TFG store the phone once I switch off no matter what it will switch on after two days I sent it back to them it's been 2 weeks still not fixed I tried to call them , they no picking up I tried today again they answers after 30 missed call telling me they were busy assisting customers as if I am not a customer, they said I must come and take my phone but it's not fixed because I have pass word on my phone I told the lady but I gave you my password she told me no I must totally removed it mind you it's been 2 weeks they never told me that