hi guys I am a complete noob so I got some questions before I do anything to my watch.

Model Number: SM-R750
Software Version: R750XXU2B0G2

so the watch is from Asia and I have paired the watch to a Samsung galaxy note 4 everything is in English apart from 4 apps.
I plan on using the watch with the sim card 1st off can I change the firmware to the uk firmware?
and will the sim still work ? make calls and texts ect?

I am new to this what are the steps I need to follow?