As stated by Stef previously, this is a charge for security services provided by Frontier Secure on behalf of internet service providers. AT&T asked me if I wanted this service (which I'm surprised, they typically add additional services with no acknowledgment). I explicitly stated I did not want the service, but it appears they persisted in adding it to my account without my permission.
The number I called was 888-620-3663 as provided on the credit card charge. They had on file an account with all my information. I requested a cancellation and refund for the two charges I incurred ($2.99 and $12.99). I was a little steamed, but the rep was very nice and obliged my requests with no protest.