Managing the loan or lease: Vehicle loan or lease

My husband and I consolidated our debt, which included a payoff of our lease. During the process, which took several weeks, and automatic payment went through, resulting in an overpayment of the total amount due. We overpaid the lease by more than $500.00. I have asked that this money be returned and was told no, they hold onto it until the lease term is done ( nearly a year away ) in case there are any damages they wish to apply it to. I do not see how they have the right to withhold my own money on account of a future hypothetical cost not yet due.