If you have Plus on your account as well as a state, or two state returns on your account, that could explain why you are being charged twice. Both Plus and the state return cost $29.99 on Federal Free. You can remove the charge (s) by removing the offending program.
How to remove Plus:
https://ttlc.intuit.com/replies/4241405
How to delete a state:
https://ttlc.intuit.com/replies/3301384
