IRS took money from me that was already paid to them, how can I fight this?

I paid in full to the IRS money they said I owed them from working at Gold's Gym in 2012.  I paid payments using my husbands credit card and from our personal checking account.  Then once it was paid in full about a month later I got another bill for the SAME AMOUNT.  How can they keep billing me when they took my payments?  How can they take it from my refund again?  AND THEY DID!