sim900 gsm sheild is not working

I'm using following gsm sheild but its not working at all i tried to send receive msgs,calls but it doesnt work at all
when i make a call it says that i can not connect right now

i'm using external power 9v/1000mA also
using Arduino Uno
sim is working Checked
and not password protected

i'm struggling with this for months now and i cant identify the problem
i have already tried this with two same gsm sheilds but the same thing happens
even different Arduino uno

Post some code? And a smaller, in focus photo wouldn't go amiss.