As an Organization Manager you are able to filter the Organization Volunteers list by permissions. Under the General Organization Filters, there is a Permissions option that allows you to filter down to users that either have or do not have one or any of the permissions levels.
Using this filter can help make sure that any actions being taken include only volunteers with the correct permission level. For example, if you are trying to send a message to all volunteers but not admins, then you can filter the Organization Volunteers list to show only Basic Users.