I don’t know what’s going on but whenever anyone rings me it tells them my phone is busy or goes straight to VM. I have no one blocked, no call diverts set up, they can’t leave messages but I can call them
I'm wondering if you have Do Not Disturb Activated on your phone.
Also try putting on Airplane and off a few times and even restarting it. What device do have? Can try resetting Network Settings on the iPhone if you have one.
