Volume settings for notifications and ringtone keeps turning on after spam call Currently running android 7 on an HTC 10, and constantly having spam callers reach my number all day.

Normally when I'm working I have my ringtone and notification volume set to vibrate only.  However, whenever a spam or scam caller reaches my number (I don't pick up), the volume for my notifications and ringtone goes back up after the call is declined, so the next scam call blasts my phone at a high volume while I'm working.  I've tried blocking the numbers, but these scammers keep calling from different numbers and my phone keeps blasting sounds loudly in the workplace everytime it happens after the first!  What can I do about this, or is there a setting that I have not checked?
Never mind, turned out to be the CallBlocker app causing the volume to go back up.  Uninstalled that and installed Truecaller instead.