FlyerTalk Evangelist, Ambassador, British Airways Executive Club
Join Date: Jun 2008
Location: Somewhere between 0 and 13,000 metres high
Programs: AF/KL Life Plat, BA GGL+GfL, ALL Plat, Hilton Diam, Marriott Gold, blablablah, etc
Posts: 30,666
Whilst you can indeed try, no, you haven't understood the rules correctly (unless BA voluntarily published a specific rebooking guideline for this specific change which I am not aware of) - the airline is entitled to use a wet lease, indeed, virtually all European airlines do that.
Can I ask if there is a particular reason you want to change? The service you'll get will be exactly the same as you would on BA (this is not a codeshare, just a wet lease), only the plane will look different but for all you know may well prove more comfortable than some of BA's own!