Although there is no fee, a name change will result in the prevailing rate to be applied to the new person.
Also, this is only possible to passengers 2+. The head person cannot be changed. This will result in a completely new booking.
For example, if you change passengers 2+ under an on board booking, the room will still get the OBC, but the new passengers will not (should not) get the 10% discount.
Changing passenger 1, will result in a cancellation and a new booking established. No OBC, and no discount. In fact, if this is concierge, deposit will be lost as well.