Unfortunately the cooling off period doesn’t apply if booking within 24 hours of the flight. So unless the fare you booked was refundable you wouldn’t have been entitled to a refund.

In fact had vouchers (FTV) not existed the most you could have got back if non refundable was a small amount of taxes and fees. The voucher at least allows you to preserve the value and use it towards a new booking for travel up to end September 2023.

EDIT: my apologies, just noticed this is your first post so a warm welcome to FT, sorry it’s not a nice issue that has brought you here.