Is it possible or possible to add a function to replace unusual letters with standard ones?
In Polish, there are letters such as Ą Ł Ó Ż and a few others, the same as in many other languages.
In other phones, there is a setting in the SMS application that allows you to change these letters to normal ones automatically before sending the message (replacing them with A L O Z). Then much less data is sent, because these types of letters take up much more bytes.