Multiple people have been posting about this - short version: you should be able to get the MM refunded. Many people are reporting doing it over the phone by calling ticketing, Option #5. I just did that and was told that since I have not upgraded our vouchers yet, that they cannot process the refund over the phone but I need to do it at the guest relations window when we redeem the vouchers. So, you can try calling ticketing and see if you have better luck than I did.