There is a way to filter those who are no longer receiving notifications?

Hi there, yes this is done automatically actually. Once a user unsubscribes our system detects this and marks it as unsubscribed to remove from further sends. You can also delete users that have been inactive for a long time so they do not get included in further sends as well. If you have any more questions or need further assistance with this, feel free to reach out to support@onesignal.com we would be happy to help and continue the conversation there.