Low in-call volume in my Hyundai Veloster with HTC one M8

[AC Question]

Hey Guys,
I used to have GS3 and I liked the phone a lot. I switched to HTC M8 and the in-call volume in my car is really really Low. it plays music through bluetooth just fine however.
I have linked other phones in my car, and I have this phone with other bluetooth devices and the in-call volume wasn't bad.
I tried re-pairing it and made sure all the levers are cranked to the max, still the call volume is really low.
Any thoughts or suggestions I could try? any apps (or ROMs) out there that can boost call volume? Using it in car for making calls is essential....

 

[B. Diddy]

It might just be a problem with the car's Bluetooth software. There can still be compatibility issues. It may be worth going to a Hyundai dealer and asking them if you can try pairing your phone with another Veloster on their lot, and seeing if the call volume is still low.