Poor customer treatment.

I bought a Samsung Z flip from four ways vodacom shop. The phone was just draining battery even when I am not using it. I put all apps on sleep mode, put the phone on dark mode it kept draining. I returned the phone to shop, they say they will take it back to check it out. We'll they call me back to fetch phone and say it's background apps, this is complete lie because the phone was even hot when I am charging it. I feel like they should have given me a new phone. This unacceptable.