Professional
There is actually a huge difference between using a mobile phone and talking to a passenger and this was clearly shown by research done by TRL (Transport Research Laboratory UK) in 2007 which showed that the use of any mobile, including hands free, resulted in a serious degree of distraction far greater than talking to a passenger. The message is clear - using any mobile is best avoided. If you really must take a call on hands free, make it very short: "I'm driving, I'll call you back when I stop". End of call!