Did a purchase on November 18th with an overpaymen...

Did a purchase on November 18th with an overpayment of $250.00 I was told it will be refunded by the end of the week as of today December 30 after many calls to the finance and accounting Office no check, no refund every time that I called and get transfered to accounting noone answer the phones I have left voicemails, my name and phone number with the main office, three weeks ago I was able to speak to somebody who told me that the check was in the mail obviously it's not.