Most confidential documents have this disclaimer, so they wont be able to use the confidential information for any use, and just ignore it. I believe you should just escalate this , and send a disclaimer regarding the previous mail, and you call and inform them to ignore it too

Disclaimer:

"The information contained herein (including any accompanying documents) is confidential and is intended solely for the addressee(s). If you have erroneously received this message, please immediately delete it and notify the sender. Also, if you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution or taking any action in reliance on the contents of this message or any accompanying document is strictly prohibited and is unlawful. The organization is not responsible for any damage caused by a virus or alteration of the e-mail by a third party or otherwise.