Hello,
it sounds like you may have previously missed some incoming calls. If this is the case you can dismiss the notification at the top bar by
place your finger to the top of the screen
at the same time using one finger,
tap hold and drag your finger down towards the bottom of your phone to view notifications.
Then find the icon concern in your alerting notifications. Place your finger on the notification then hold and swipe to the left or right of the screen to dismiss it.
hope this resolves your problem
Best wishes