When a transaction is cancelled, a refund of the MM fee is automatically issued to whoever paid it. It is added to your site balance and can be used towards paying the fee for another MM transaction. It can also be refunded to the original payment method used, but the refund request must be made within 30 days.
You can check your site balance and request a refund on this page:
https://www.epicnpc.com/tradeguardian/wallet