If you are composing your SMS messages in another language, you will want to change your spell check to the language that you are using so that you can write your message with correct spelling.
This document explains how to change the spell check language in the Desktop Client Software.
Open the desktop software by double-clicking on the WinSMS desktop icon.
Now go to “File”, then “Preferences”
Then select the language that you want to use under “Spell Check Language”
Your spell check will now be checking your spelling for the newly selected language.