You may not have actually gone digital yet. The August 25th date they gave you may just be the date they are starting the digital conversion in your state. It may well be a week or 2 before you are all digital.
The other possibility is that your TVs have digital tuners and don't need the converter boxes.
From what I understand, if you don't hook up the boxes and activate them within a certain time, you will get charged for them.