Thank you for your post and welcome to the Nokia discussion fourms.
Parrot's website does state the mobile device and car kit are compatible with the following features:
So there shouldn't be any issues. I know this sounds kind of obvious but have you tried adjusting the volume on the car kit and also on the mobile device?
Also have you tried updating the Parrot car kit to the latest firmware version?
You can check the latest version and updating guide on the below link:
If after updating and checking the volume level of the car kit and mobile device that the audio is still barely audible then I recommend you give the Parrot support line a ring as there website does claim the phone is compatible with there car kit.
Hope this helps.