My iPhone 13 suddenly stopped accepting calls from a friend

My phone suddenly stopped accepting calls from a friend. Her calls go straight to voicemail, which it accepts. There is never a notification that she tried calling. I get her SMS and Messages app messages. The problem has now lasted several weeks.

I have gone through all the steps I could find in this community. Her contact information did NOT say she was blocked. Call Forwarding is off. Do No Disturb is off. Airplane mode is off. I did a partial RESET of the phone (did not delete files, apps or contacts). I have tried unblocking all numbers in Settings App > Phone > Blocked contacts. I deleted her contact file. She has contacted her phone company; they said everything looks fine. Still, no calls come through.

Suggestions?

iPhone 13

iOS 18.2

128 GB/81 GB available

[Re-Titled by Moderator]