I finally found where to change my invoice message.
It currently has a message about checks and money orders with my address.
Since I no longer accept checks or MO, I want to delete that message but it will not delete it.
I can delete it and add another message but when I click on save, it pops up a non secure site message. I click OK on that and my new message dissapears and my original message appers with no changes.
What am I missing??