Gsm 900 need help.

I think i have a lot of problem.. and i need.ASAP... I have arduino uno and gsm shield 900... i want to make the gsm send sms to phone. I have a lot of question :

1) when coding, do we need to put what pin is the gsm?? If yes, what pin does gsm use??

2) when i use gsm example... send message... its stuck on sending message... and didnt run the pin number coding... it just stuck at sending message... between, the sim does not have pin number..

Can somebody guide me?? Can we personal whatsapp?? :confused:

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This friday :(

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