@higgsmum: Any missed calls should be visible in the Phone app > Recents, however if not then please head here, tap the 3 dots in the top right > Calls to Show, and set this to All Calls. Furthermore, tap the 3 dots in the top right > Settings > Supplementary Services > Call Waiting, and toggle this option on to hear a sound when someone calls and you're already on the phone. I hope this helps.
