The Fix sold us a s**** phone and they are not rectifying this

I bought a Samsung at The Fix The Grove Mall and it has never worked for more than 3 days. We have returned the phone over 3 times now, but it has never been home for more than a week. We take the phone back, they keep it for months and call us to say its fixed and the screen goes black again. They keep on telling us the issue is with Samsung, but why are they not giving us a good customer experience? Why are they not giving us a new phone and picking a fight with Samsung but rather choose to inconvenience us. If they were sold a **** phone why don't they deal with that but rather choose to make us suffer for what the manufacturer gave them?