My app must have just been updated. I used to not have this problem but now I have no control over the volume of the alert even when the phone is silenced.
I found an older thread about it ( https://community.atlassian.com/t5/Opsgenie-questions/Android-Oreo-8-1-Notifications-Always-Playing-at-Full-Volume/qaq-p/1043090 ) and support advised to change this option:
"..play Opsgenie sounds at maximum level.."
but I have no such option. Could be that that thread was for android and I have an iPhone. Hopefully the option to fix the volume is available I'm just not finding. Otherwise this is ridiculous and need to be fixed. Please help.
edit: testing turning of the "Allow Critical Alerts" option ...
edit #2: ok, that's all it was. I just need to turn of the Critical Alerts option.
This confused me because either the app update or something else unbeknownst to me turned on this option.