Apartment complex charged me double rent, but won’t refund my credit card.

I pay rent through Resident Cafe (third party portal). They accidentally charged me rent twice, and then refunded my balance on Resident Cafe, so now I have a negative balance there, but my credit card got charged both rent charges and now I owe my credit card 5k. I don’t have the money and my complex told me “since it’s refunded to my resident portal it’s fine” and they can’t just undo the charge. What are my rights here?? Is this legal?! I can’t pay off the 5k charge they gave me.