Go to settings > apps > manage apps > tap 3 dots in top right corner and select 'show all apps' > you will find Permission manager in the list > clear data
Please let me know if you have found it ;)
I think I found the solution! If you go to settings > Sound & vibration, you can set the calls/reminders/notifications volume. If you set this bar to zero, the sounds disappear, even if you enable incoming calls