Apple Support has greatly declined within the last 2-3 years. I had an intermittent WiFi issue with my brand new MacBook Pro, purchased in June 2015, and because the Wifi issue started in late August, they wouldn't switch my laptop for a new one because it wasn't a "hardware" issue. Over a year later, I had the same problem, despite hours and hours of phone time/in-store visits. Their solution to everything is to re-install the OS, which gets very annoying after a while.
Eventually, I got so tired of their incompetence that I disputed the charge on my credit card (eventually lost the dispute but I knew that was coming) so I did a complete factory reset. Whatever I did fixed the issue so now it only occurs about once every two weeks instead of every few hours.
ANYWAY...
I am having the exact same issue with the notifications on my iPhone 7. I have done the following:
1) Shut down my phone overnight and rebooted...same problem a day later.
2) Reset the factory settings on my phone...same issue two days later.
3) Wiped my phone clean and did an iCloud recovery...same issue two days later.
4) Wiped my phone clean and did an iTunes recovery...same issue a day later.
5) Brought the phone into the Apple store for a hardware diagnostic test...naturally the "hardware" is completely fine.
I haven't bothered calling Apple support because I know they're not going to be able to solve this. We're all just going to have to wait for the update that fixes this issue...if it ever arrives.
Oh sidenote: I'm actually switching over to Android after my lease on the iPhone 7 is up. The only thing stopping everyone from having an Android is the simplicity and user friendliness of the iPhone. I've had it with Apple and their decline in their products.
Good day.
EDIT: I bet even if I do decide to call Apple support, they will make me run though the steps I have listed previously "so they can have it on record that I've done what they've asked."