Cheap September 2021 Flight Found... Flexible Ticket Help

[Aimee_K]

I've just found the below economy flight on the British Airways website

Outbound
London Gatwick To Orlando
Wednesday 8th September 2021 10:35am

Inbound
Orlando To London Gatwick
Wednesday 29th September 2021 16:55pm

2 Adults with a 23kg checked bag per person

£879.76 (£439.88pp)

This says that this is a 'flexible fare'.
All I can see is to cancel the booking its £15 online or £30 by phone. To make changes online it's free but £30 on the phone.
Then it says:
'Time/date changes permitted at any time before each flight departure for a change fee of GBP 150 or an upgrade fee of GBP 150 plus any difference in fare. All sectors may be repriced. Changes subject to availability. Fees apply per ticket'

My question is does anyone know what 'changes' are permitted to be done online for free? I can clearly see it states if I wanted to change the flight time or date it would cost me £150. I would also assume that if I changed a passengers name there would be a charge possibly.

Apologies if I'm being stupid here.