Thanks for the reply, unfortunately both those links only refer to problems with connecting and playing audio via Bluetooth, nothing about outgoing audio, the microphone. My phone has no issue connecting and playing music etc, it's just on calls the other person can't hear me. I am a little confused tho, when a call comes through via bluetooth, which one picks up you're voice, the phone or bluetooth device? This is why I originally thought the issue was with the mic in my stereo, although it was bought new and Halfords were just as confused as me, but now I know the same thing happens when linked to my home speaker, which has a microphone that I know works and I had my phone in my hand when I answered and the callers voice came through the speaker, as it does in the car, but they couldn't hear anything?! It's so frustrating especially in the car!