Originally Posted by
Jimmyco
It's an eVoucher technically, not a Future Travel Voucher.
If it is from a booking which you decided not to take over the last two years and you applied for a voucher, then it's a future travel voucher.
There are two types, offline FTVs and online ones. The online ones are in the form of an evoucher.
Regardless of the type, you can't use FTVs to pay for changes/upgrades to existing bookings.