Bluetooth Phone Echo

Over Bluetooth, during "hands-free" phone calls over the car's mic / speakers, on my iPhone 6 / P85D, the other person can always hear themselves. This is 100% of the time. Does anyone know what's going on here? Phone and car are on the latest updates, and I've tried forgetting the BT connection and re-establishing it.

Any tips or tricks to correct this?

Thanks!

PS - as a side note, I cannot hear notification sounds on my iPhone 6 when it is Bluetooth connected to the car; those notifications will not make any sound over the car speakers or the phone itself until I'm out of range of the car, or I disconnect the BT link.

I had my car in for other service and I mentioned this issue. It turns out that the issue was caused by one of the mics in the car being misaligned. They re-aligned the mic and the issue is now gone.