Disable Autocharge via API and update retry date

Hi,

Here is what I’m trying to do via API:
Turn off autocharge for all existing (and future) subscription orders and then schedule my own retry date & time for failed orders (declines).

Autocharge is already turned off in the Billing Settings at the merchant level. However, any existing subscriptions are still set to autocharge. How do I turn off autocharge for these existing subscriptions?

As for setting a retry date and time, this is the current situation:
I set a failed order to retry tomorrow at noon. Then, 5 minutes from now, I set the same order to retry at 1pm. InfusionSoft will retry at both noon and 1pm.
How do I update the next scheduled retry (as opposed to adding a new retry)?

Thanks!