Message Delivery Issues after iOS 18.1.1 Update

iPhone 15. After update to iOS 18.1.1 texts won't deliver randomly, calls won't come through, internet browser works intermittently (Safari). I asked Apple Support for help. They had me hard reset the phone. Then the network settings. Then all the settings. Didn't work. Then my phone told me I was no longer signed in to Apple ID and iMessage. I got logged back into those but still the internet would only load pages randomly, some messages will go and some wont to both other iPhone and android users, and when my mom calls me from her iPhone the call drops and then she can't call back. Apple support had me run a device diagnostic which told them all was well. Then they signed off the chat as if that was it because the device is supposedly fine. Here for any ideas. I wish I could go back to 17.

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