I’ve struggled with delayed call and voicemail notifications for years.
A phone reboot or airplane mode toggle or network reset would show the missing notifications….but subsequent missed calls/voicemails would not appear.
After many wasted hours of support calls and store visits with no resolution, I finally found the source of my problems…….too many visual voicemails!!!!!!
PERMANENTLY DELETE ALL OLD/LARGE VISUAL VOICEMAILS!!!!!!!!
After removing ~100 visual voicemail messages, I now get immediate missed call and voicemail notifications.
I am so happy!!