post https://www.ted.hover.com/api/vouchers//cancel
Cancelling a Voucher may be something you wish to do if your customer cancels their account with you and hasn't yet redeemed a Voucher that had been given to them previously.
Once cancelled, a voucher is immediately invalidated and can't be used. If the user attempts to use the Voucher after it is cancelled, they will see an error message that indicates that the Voucher they are attempting to use is not valid.