I have a MacBook with High Sierra. I can't get rid of the FaceTime audio notice. The call was answered on my iPhone and is long ago disconnected. I want the window notification gone. What will work?

I found something that worked! 'Open Activity Monitor and search for FaceTime. Then select FaceTimeNotificationCenterService, press the red circled button and choose Force Quit." Thank you, "Qbyte"! (I was going to use your third suggestion but the url link didn't work any more. I don't use FaceTime on my computer usually so I may not have a problem with that FaceTimeNotificationCenterService being removed. I'll keep your quick fix for future use.....