I have a Nokia-3 handset.
On the 'phone' icon, there is a red number 1 which indicates I have one missed call. However, I deleted all of the missed calls, force-stopped the phone app, and did several restarts; but the red number one will not disappear (4 days now!).
This exact same thing/error happened with Hotmail and What's App a few weeks ago and members on the forum kindly helped me to resolve it.
Many thanks in advance,
Try uninstalling the updates of the phone app by going to settings> apps> phone. You can update this app again by going to Google Play Store. Have you still not got the Android Oreo? This issue has been fixed in that version of Android.
I thinks its worked.
I was told that the Oreo update would be 'automatic'. But no, I am still on the older version.