I have been experiencing occasional delays in receiving text messages and voicemail notifications.
Occasionally, text messages will not be delivered to me for several days until a flurry of texts arrive all at once. This has happened intermittently over the past year or two.
Additionally, today, I received a voicemail and was surprised to discover an unread visual voicemail from June 25th. It was a friend calling to inform me that she was in the hospital and she was reaching out for my support. 18 days had passed, and I never received a notification that I had a voicemail and my call log has no record of a phone call from the number that left the message. This is obviously extremely distressing.
Please help me to understand why these errors are occurring so that I can take steps to have them remedied. My phone is always on, with data turned on. I reset my phone about once every other week and install all updates once I receive notifications that they are available. I do not turn on "Do Not Disturb" and have set call and text messages to override "Do Not Disturb." I checked my settings and notifications are turned on (however, most "Advanced options" are greyed out). I have two sim cards and purchased my phone (OnePlus 7 Pro) in 2019.