How can I remove sos of my phone top right hand corner ?

This article gives some more information about when you will see SOS. If needed, it has additional steps for reconnecting to your cellular network.

If you see No Service, Searching, or SOS on your iPhone or iPad - Apple Support

"If you see No Service or Searching in the status bar on your iPhone or iPad (Wi-Fi + Cellular), your device isn't connected to a cellular network. If you see SOS or "SOS only" in the status bar, your device can still make emergency calls."

SOS can mean a couple of things

Your phone provider does not have coverage where you are, but another provider does, and so you can make SOS calls which will be made via that other provider.

In my experience, when I know I should have coverage, I get SOS when my phone provider updates some settings, and restarting my phone fixes it. After restarting the phone, I get 4G or 3G back.

So I'd try restarting your phone and see if that fixes it.

You will need an active cellular service on your iPhone and that will replace the SOS.

Axel F.