...
Sync Disable Package Component: disables the package from syncing to the Account's Bill Day. When the sync disabled User-Package is created it will be configured to billed based on the Effective Date of the User-Package. E.g. if you add a monthly billed package to a user on May 10th it will bill for the first month on May 10th and continue to bill for the package on the 10th of subsequent months
Additional Billing Item Component : allows you to add a one-time or reccurring recurring charge tied to a package but the charge is billed based on it's own specified bill date, not the package bill date
Sync Disable System Wide : allows you to disable bill date synchronization entirely so that packages can be billed on different days, or enable a mixed synchronization + prorating approach
...
Load the customer account and click the linked bill day number on the left sidebar (in this example "9")
In the bill cycle edit page that loads enter the day of the month you wish to bill the account on going forward
Click Save to commit the bill date change
...