UNO + GSM 2 shield no sound on audio out

Official Hardware Retired GSM Shield
1

Dear All,

My new purchased GSM V2 has the following problem:

  1. SMS receive and transmit => OK

  2. Make voice call:
    can makes the connection, ring tone can be heard on the cellphone but both sides are no sound.

The Voice call program is download from this url:

  1. Receive a voice call:
    Incoming ring tone can be heard on my earplugs but again no sound (both sides).

The Receive voice call program is download from this url:

I have tried two sets of mobile phone earplugs with microphone (L-R-Gnd-Mic, CTIA standard) but the problem persists. I've also tried to use the stereo speaker (L-R-Gnd) to listen but still cannot hear any sound.

Pls help.

Many thanks !!!