I bought cellular radio module, I connected a microphone into the “mic” and the headphones into the “speaker”, making a voice call, you will hear the voice of the receiver but he did not hear me, I tried to change the microphone but not heard.
Is the card defective?
I connected Audio out from the audio module and played some wav files over the cellular module… Sound came trough to my phone. Maybe it don’t have mic amp on board…try playing audio from an MP3 player or something like that, connect headset jack from MP3 player to mic input on cellular module. You should be able to hear audio then (we did).