With iOS 10.3 a bluetooth issue is present where the audio of phone calls is not routed to the bluetooth device. In my case this is a BMW. When setting up a call from the bluetooth device iPhone shows that audio is routed to the iPhone itself in stead of bluetooth device. Microphone and speaker of iPhone are used. Audio of phone calls is routed to bluetooth device only if manually switched from iPhone to bluetooth device. Issue: Music audio is routed correctly but audio of phone calls has to be switched always manually to the bluetooth device in a BMW. Problem was not present with IOS 10.2 and 10.2.1 for myself.