Samsung S8 plus a disappointment and is dangerous in my opinion

Samsung S 8 plus is a real disappointment for me , I have had my phone for just over seven months .Samsung did a screen replacement 24th November 2017 .I found the phone battery to not be lasting ,I called the Samsung repair guy to notify him , he was on leave and would sort it out when he came back , I said no problem and he has always been a very friendly guy .Sunday just past my phone starts cutting out and battling to start ,I called him Monday again ,he said they would come through to me Wednesday. While waiting for Wednesday it cut out Monday ,Tuesday and Wednesday , When they arrived to fix my phone on site Wednesay afternoon(yesterday) , they removed a cellphone protector cover that cost me R600 from MTN . WE found that the back of the phone was pulling away from the front of the phone. Something to do with the battery he told me ,and the driver says ma'am you lucky the phone did not explode . Also we cant wont on the phone in this heat and all the machines to work on this problem is at the office. The phone is not safe ,now they want to fix my phone and send it back to me ,I truly feel sick to my stomach that a new phone can do that ,I have had a cellphone the last 28 years and this has never happened . Samsung needs to replace the phone , I am not sitting with a phone that is unsafe ,I use my phone a lot because of community involvement . Samsung I am truly disappointed and I do not want a phone that is unreliable and dangerous in my opinion. Samsung sort this problem out please ...