The details you provided, @Herwig0 , make it pretty obvious for any, I hope, reader that you set too low nightly prices and you meant amending those rates. There is no trace of reservation updates in the sense of actual changing other details than the nightly rate per person. So @Emiel1's answer was clear - you can't do it. In this context I would've replied in more or less similar way. You see, in some geo locations we tend to get straight to the point. Other locations invented legal suits against wet floor. It's all about the diversity Airbnb promotes, and tolerance.
@Matthew285 seems to have provided you with some extension to the topic of changes in general, not necessarily applicable in the case you presented. Another trick is that knowledgeable hosts can escape unprofitable reservations by increasing their prices in the meantime when they see an alteration request from a guest. Thus the updated nightly rate will apply.
// "The only person you can trust is yourself"
