A20 and modem gsm olimex

[zaina]

 can somebody help me i have olimixino A20 and a mod gsm olimex i am tired to send sms but it dosn't work i follow this toturial http://olimex.wordpress.com/2012/10/12/using-mod-gsm-with-imx233-olinuxino/ there was no error but the sms is not sent ... i want just know if ther is configuration should i do before start  ... is it necessary to install ppp ?? thks