Samsung — Company Refusing To repair my phone under warranty

I am using Samsung Galaxy A71 and my phone is under warranty, i have given my phone to service center to update software and they accepted my phone for software updation but now they are saying your Motherboard is broken, they brake my motherboard and now refusing to change it under warranty. Service centre not take my permission to open my phone i submit my phone only for software update but why they open my phone hardware without my permission. There is no any physical problem or any damange in my phones while i submmited they broke my phones mother board and now refusing to change it under warranty. This is my job sheet number in samsung care [protected]
Please do something for me.
Thanks