Can't Speak into my IPhone 3GS

Hoping someone can help me.
I have an updated IPhone 3GS,06.15.00 baseband running 4.3.3.

Everything is working perfectly fine except the voice function. For example, when someone calls me, and I speak into the mic, the person on the other end does not hear me. As a result, voice memo and voice control also doesn't work. Does anyone know how I can fix this?

If not, does anyone know how to downgrade the 06.15.00 to a 05.xx.xx baseband? My phone is still under warranty and I need to downgrade it to bring it back to the apple store to get a new one. Any info would be highly appreciated.

Welcome to Mac-Forums jcheng

Usually this problem is resolved by plugging and unplugging headphones/ headset into the phones jack a few times and it kicks it back into the right mode for speaking into the mic and all should be resolved.

Hope this works for you.

- Simon