GSM Shield says message send but doesn't receive

Hi, I'm using a gsm shield to send SMS messages, and I'm literally on the first step with the info at
I used this code :

Code: Select all #include "SIM900.h" #include <SoftwareSerial.h> #include "sms.h" SMSGSM sms; int numdata; boolean started=false; char smsbuffer[160]; char n[20]; char sms_position; char phone_number[20]; char sms_text[100]; int i; void setup() {     Serial.begin(9600);         if (gsm.begin(9600))     {         Serial.println("\nstatus=READY");         started=true;     }     else         Serial.println("\nstatus=IDLE");     if(started)     {         if (sms.SendSMS("+300000000000", "Arduino SMS"))         {           Serial.println("\nSMS sent OK.");         }         else         {           Serial.println("\nError sending SMS.");         }          } }; void loop() {     if(started)     {         sms_position=sms.IsSMSPresent(SMS_UNREAD);         if (sms_position)         {             Serial.print("SMS postion:");             Serial.println(sms_position,DEC);             sms.GetSMS(sms_position, phone_number, sms_text, 100);             Serial.println(phone_number);             Serial.println(sms_text);         }              delay(2000);     } };

When I first started .. the code runs in the case of a transmitter and receiver, but now can not receive .

pls help me .  :'(