Non-iDrive Bluetooth Mute

[02rsxpilot]

I frequently begin conference calls on my iPhone 5 at the office and then walk to my car to finish the call on the road. I mute my phone except for when I need to speak. If I get in the car with the mute on, the phone pairs with my bluetooth but the head unit does not say the phone is muted. If I need to speak then, I'm not sure if I can hit the mute button on the head unit or if I'll need to do it on the iPhone (much harder while driving). If I hit the mute button on the head unit, the display will then say my mic is muted, which is the opposite of what I want.

Basically, I'm confused why whatever mute setting is on the phone when I enter the car doesn't carry over to the display of the head unit.

Anyone have similar experience or know a workaround? Should I just unmute my phone prior to getting in the car? (This may subject the others on the call to my Beemer unlock beep and engine starting noises...)