Someone's got to be first to be interviewed! What are the aspects of tbe interview for which you feel unprepared? If I remember rightly from other posts, you're going for a commission. And how much leeway are you looking for?
You can ask for a change, but there might not be much flexibility. The AFCO has timelines to meet and will have some things set in stone during the working week like the day for AST or processing final interviews.