Standard Message Status Delivered Comments

My question is similar to a previous post but I am not sure if I should make the same changes. I would like to put a standard message in the comment area of "Delivered (3)" Status that says- Thank you for your order! It has been shipped today by First Class Mail. Any problems or questions after the sale, please contact us at 309-663-2564 anytime. Thank You, Chuck"

I have to keep writing something in the message area when I update the delivered status. If I don't, the message the person gets on the other end makes them think it has already been delivered to their home. I have had several contact me just to say they had not received it yet. Thank You