sim unlock s8 plus

your device may not be locked.
you need to go to Sammobile webpages and download the OS specific for your device and country. then find the instruction on how to use your PC and Odin to apply the new OS.

no root is needed ever if only you need to replace the OS. but yes you can use Oden to root your device not recommended.

I can use all Samsung security app...and get all officials update???

thanks for replay

please follow this link.

https://www.xda-developers.com/how-to-install-android-oreo-on-the-samsung-galaxy-s8-s8-exynos/

thanks for your help....but i contact samsung customers service and they give me unlock code...help others with this information...