They don't deny that I paid on March 1 (and I have my credit card statement to prove that). They're denying that I didn't have to pay anything on March 7, and they applied my March 1 payment to March 7.

I honestly don't care how they fix it--make March 1 no charge, credit my account, whatever--I just want them to fix it so they stop telling me I owe them money that I don't.