iPhone 11 Pro Max return/exchange

Hello there, I bought the 11 pro max 6 days ago, after 2 days of using it the phone would get super hot while charging and even if not on charge, also the battery was draining super fast even with app refresh off. So took it to the apple store and they did see and felt the phone super hot and exchanged it with a service unit. well 4 days later and they service unit I got is doing the same thing, I told them that and they said I had to set it up as a new phone and not download my back up even after doing this its getting hot. I asked for a return and they told me Im not allowed to return it because they already did a swap with the first one I bought so I had to stick with this one and Im still in the 14 days for returns. has anyone been in a same situation? is it true they cannot make a return because they already did an exchange