It probably won't hurt to ask about a refund in the meantime anyway. You may find that some of the non refundable aspects were suspended. They probably won't be able to tell you the amount over the phone as it's been issued as a voucher (presumably +10%) and part used so will need to go to the ticketing team to calculate. I made a similar enquiry via the twitter team back in 2020 and they came back a week or two later with a figure. But like I said, be sure to say that you are only enquiring what the refund amount might be at this stage, in case using it up on a new ticket is better value for you.