I have a Samsung Genio qwerty mobile on Vodafone

I drive around a lot and have a parrot hands free system in my vehicle connected via Bluetooth


My problem is if I am on a hands free call and another caller attempts to contact me I don't know they are trying to contact me,but when I have finished the call I am on , then a missed call message pops up on my mobile screen

The caller trying to get me just gets the normal ringing tone , it doesn't play an engaged tone or alert me to the other call coming in
But I did notice on Friday the Parrot screen actually flashed up with the name of the caller trying to get through but couldn't as I was on the other call

This second caller commented that as it was ringing normally he could not understand why I didn't answer the call as they know the phone is always on 24/7 and in the hands free mode whilst driving or in my pocket when not driving

Short of looking at the Parrot screen how can I be alerted if another caller is trying to get in touch ?

Any help ?

Cheers