A6 GSM/GPRS Demo V6.0 interface

Hi fellows. I just got an A6 GSM/GPRS Demo V6.0 board to interface with an Arduino UNO. No problem to interface but to make the A6 works. I have read other forums and almost then say the way to test this board is to make a call to the SIM card number placed on the board. I had power up the board with an external 5 Volts power supply and when I call the number on the SIM card the only signal I heard is a busy line.

I put the pics of my board
Any one see this issue before?
Any help will be really appreciated.