@Tajana2 , hold it: so you do have a confirmed booking, yes? and after that, someone, you or the guest, sent a "change reservation" form - that is the only thing that counts. if that was not accepted within 24 hours then it all goes back to the original booking. seems strange that yiu would send a change of reservation for actually 100 less, and guest would not approve it?? I mean that's in their own best interest....
Or are you talking about an agreement reached per messaging back and forth? all that is informal talk which means nothing until there is a definite booking request/confirmed booking.
Sometimes we hosts get the run around from potential guests - and nothing ever materializes.
So I'm curious: what exactly is going on in your situation?