problem in connectivity for gsm 800

im doing a project on vehicle tracking. as per the requirement i have to send an sms to it and it should give back reply containing the link to the location on google map.
but im not any type of reply!!
what should i do??
i have attache the circuit diagram and the original pic of the project as the way i get it
please give me the solution
and i hve also find out that the gps receiver shown has 6 pins E G R T V B but in the circuit diagram it is using only three of them !!

Circuit Diagram.pdf (30.7 KB)

can anyone tell me how do i receive message using this gsm ??
which port should i connect this??