Unable to unblock phone number

I have an iPhone XR with IOS 13.3. The phone number of one of my friends has become blocked and so I do not receive her phone calls. She is able to leave a voice mail, which shows up in "blocked voice mail". So I can get my messages from her and then call her back, but I have to remember to look for those messages.

Since I'm getting her voice mail messages, it doesn't look like her phone calls are blocked by my carrier.

I've tried to unblock the number by going to Settings > Phone > Blocked Contacts, but her number doesn't show up in the list. I've also gone to her contact to see if it shows blocked there and it does not.

This is super annoying. Can someone please help?