@Darlene169
I think all your actions on the Resolution centre are listed here:
www.airbnb.com/resolutions
I do not know if there is an option to retract (as i never asked a guest for extra money)
But the guest can decline the extra charge within 72 hours after submission, then you can decide if you want Airbnb involved (i guess you will reject that option).
best regards,
Emiel