I have a 2014 Mitsubishi outlander sport and I can connect via Bluetooth and I can make calls via Bluetooth but they can not hear me when I can hear them.

 

Does the BT voice commands work? If not then check the microphone connection, it is located behind the ceiling lamp holding panel.

If voice activation works then it is another bug in that crappy designed system. I have no other suggestion except throwing away BT module together with stereo unit and imstalling non-OEM one.