AT&T ActiveArmor Protection Security causing iPhone/Android calls to go straight to voicemail

My iPhone was going straight to voicemail without ringing, except for two contacts who could get through (MY FAMILY on the same acct but other lines couldn't get thru either). There were no alerts, and all settings (Do Not Disturb, Airplane Mode, Call Forwarding) were turned off. I reset the phone to factory settings five times, but the issue persisted. I also reset the voicemail, deleted and recreated the eSIM, but nothing worked for three days. FT, text were working fine.

Finally, AT&T's phone provisioning team resolved the issue by refreshing the AT&T ActiveArmor Security settings then it works.

Although this happened on an iPhone, the issue can also affect Android devices on AT&T.

[Re-Titled by Moderator]