Samsung Note 20 ultra weak battery and overheating battery

I purchased a Samsung Note 20 ultra. The battery last for less than 5hrs without playing videos or games and it is overheating. It is very new I took it back to centurion mall Telekom LUTENDO the manager insisted that they will fix it instead of giving me a new one. It is on contract I am paying for services I am not receiving she took the fone she said she will send it to where they will fix it I told he all I wanted was a new smart phone that's the reason I upgraded. I am paying Telekom for a smart phone I dnt have and the so called new will be a fixed one.