Upvote:0
Your ticket appears to be a Basic Economy fare (endorsed BELH which stands for "Basic Economy Long Haul").
Google Flights generally doesn't search Basic Economy fares, plus it's likely that they won't be offered these fares for a new last-minute booking (as opposed to a change) even if you tried via the BA website directly.
Upvote:2
Just speculating: you might got lucky here. Typically you pay the change fee and the difference in ticket price. Your flight is only 2 days out, so for a new ticket your are only eligible for fare classes that don't have a "must be booked XXX days in advance" condition.
It's possible that your earlier booking date enabled you to maintain the initial lower fare class and you only need to pay the change fee.
The new tickets seems to book into an "H" class for Economy, which appears to be a flex ticket with 100% point accrual, so it's an expensive one. I don't know what fare the class of the original ticket is, but since OP has to pay a change fee, it's unlikely to be a flex ticket.