You can change all livestream parameters up to 30 minutes before start.
Do you want to change the start time? Or reduce the number of cc viewers? Or activate the chat afterwards? - No problem.
What you have paid too much will be credited to your wallet, any additional payment you can pay online.
Important: The procedure RTMP Push (you send a stream) to RTMP Pull (you pick up a stream) cannot be changed. Here you have to delete the created livestream and set up a new one.