If you continue working after being told that you have to pay a deposit for a badge, your continued employment can be taken as implied ageement to pay the amount: when you do X (e.g. work) knowing you'll have to pay Y, you have agreed to pay Y. Therefore, if you told that there would be a deduction for this deposit and you do not quit/resign after that, you have consented to the deduction. If you do not return the badge, they don't have to return the deposit: you get the deposit back on return of the badge. If they don't return it, you could sue them, such as in small claims court acting as your own attorney (pro se; in order to save on legal fees) for the money.