Trust me, unless your trying to get a different mic for another reason, get it simply to make the bluetooth work or work better rather it's not a Microphone issue, unless of course you damaged yours.
The problem is in the device itself or rather the blue tooth software revision that is in the device.
The way you can tell if your mic is bad, try out the voice recognition. Use it with your ipod etc or try to make a call by using the "call ###-###-####
If it can pick up those commands and understand you properly but with bluetooth voice calls the person you're calling can't hear you, there is your proof.
I've said it a few times, blue tooth was very flakey and unreliable until I did a software update on my phone.
So, try that as well.
Just my understanding of the situation, hope it helps.