These things can sometimes take a little longer than expected unfortunately. Reimbursement processes can be notoriously slow, especially where it is a one off payment.
If you haven't received it again by end of play of Wednesday, I would call them again. If you need the money reimbursed urgently, then call them today and explain that it getting the reimbursement is important or that you may receive additional bank charges etc if its not paid back soon.
Did you attend an in person event for Willkie or was it an interview?