If the user is assigned to a role that has No Alerts selected but is still receiving Alerts, check the sites they are attached to. Follow the below steps to ensure they are not attached to a unit that is set to receive Alerts:
Click the Admin Cogs
icon.Click Organisation Administration.
Click Users and locate user.
Click Associated Units tab.
Then go to Roles to check which Alerts require amending.
Listed will be the Roles the user is attached to, you can amend the alerts on a role.