H1B Reschedule - first time traveler after amendment

I have existing H1B stamping appointment in Apr 2023, my visa expiring in Sep 2023. I’m trying to get the slot rescheduled to prior date, but i’m getting availability displayed only after Oct 2023!! Cant we reschedule appointment to a prior date ?

Is cancelling & rebooking the only option left? if yes is it advisable to cancel apr 2023 appointment and start looking for prior slots?

Since i have appointment booked already, couldn’t even see any any slots opening up in other locations. Is there any way out?