Is it possible to change the sensor hub ic at samsung service centre?

how to roll back to marshmallow???? after upgrading to oreo I'm facing a lot of problems in my s7

after uprgading to oreo I'm facing network freezing issue on s7.. When trying to call suddeny the network freezes and I can't make or receive call as well as can not use internet also...then I have to turn the flight mode on...after turning off I get...

what is the warranty period of battery of galaxy s7?

why all the time in s7 all the apps use mobile data even when data saver is on and also restrict background data is also on ?