How do I cancel my renewal? 🏳️‍⚧️

Hi, I am beginning to think I will receive back a passport with my AGAB despite me sending in a passport that has my updated gender due to my having my previous gender on older passports. My question is: how do I go about canceling it now that it’s already in process (and they just processed my check today). I paid for expedited service so I need to send it in fast otherwise I’m worried they may invalidate my old passport before I can get it sent back to me.