Please note that only the following list of ASCII characters will be treated as GSM (i.e. Normal), all other characters will result in the message being treated as a Unicode message:

a-z

A-Z

0-9

~!@#$%^&*()-_=+][?<>,’.”:/\{}

(whitespace)


If your message contain even single unicode character (e.g. £) then it will be treated as unicode to display message properly on handset (because it's encoding is different).