What was the original post ?
Anyway, the 24 bit Mode S address is programmed into the XPDR and not adjustable by the crew.
However the Flight ID, as part of elementary surveillance, is set by the crew and is normally the flight number or the tail number. The XPDR control head will normally default to the setting on last power down, hence it is possible to overlook changing this but unlikely if correct SOPs are in place and adhered to.