I'm leaving my company. Is there any legal defense for not paying back Relocation itance?

A Lump Sum of cash was paid out to me in november, before I signed any such agreement to repay relocation istance, though it was layed out in the relocation policy that I would have to repay any monies given me, it also specifically called out this "repayment agreement" doent that I had NOT signed until dec and said that no money or istance would be given until this doc was signed. So, does it matter when I signed the "relo repayment agreement" called out in the policy, versus when they actually gave me money? Or not? Am I just screwed either way.