I own BMW R 1200 GS with BMW Navigator V. I have connected iPhone 6S plus with 20S; After I connected the headphones Sena20S with BMW Navigator V; then HANDLEBAR REMOTE with 20S; Finally IPhone with Navigator V.

My problem is this: When I get calls the sound I hear in the 20S headphones is almost incomprehensible.

How do I fix this?

iOS iPhone 6S Plus: version 9.2.1

Firmware Sena 20S: version 1.6