You can authorize character transliteration by checking the corresponding box.
Transliteration consists of replacing one character of an SMS by another when that character is not taken into account by the GSM standard.
If transliteration is authorized, each character that is not taken into account is replaced by a GSM character when the message is sent. For example, the letter "ë" is replaced by "e". The message is therefore slightly altered, but the character limit will remain the same.
When transliteration is not authorized, each message that contains characters that are not taken into account is sent in binary format (Unicode): all of the characters are therefore sent as they are. However, the SMS messages using Unicode are limited to 70 characters (or 67 characters per SMS for messages sent in multiple parts). If the maximum number of characters is exceeded, several messages will then be sent, which may create additional costs.