Scirocco Central

2011 Scirocco- Was hoping someone may be able to point me in the right direction. I've recently swapped from a RNS510 to a RCD510 (RNS510 was stolen). It was a straight swap and everything appears to be working fine (aux, sd, media in and bluetooth phone function) except the actual microphone. From the digging around i've done, i have a bluetooth module under the drivers door. The unit connects to the bluetooth fine and i can hear other people but they cannot hear me. I understand that maybe this is due to the original wiring in the car being setup for the voice activation button on the steering wheel? At a loss as to what cables will need to be swapped over.

Any guidance on how to tackle the issue would be great!