To update a member's payment amount or date, visit your All Customers section > Participants > Programs > and click on the student's name. This will open their Program registration page.
Open Enrollment Structure
For this structure, click the pencil icon next to "Membership Fee":
From here, either update the Membership fee amount or the next payment date or both:
PLEASE NOTE: for Open Enrollment Structure memberships, when editing payment date, the system will adjust the recurring payment schedule moving forward. (For example: if you adjust a monthly payment from December 1st to December 15th, the following payment will be on January 15th).
Custom Memberships/Start/End Date/Etc.
For other membership types, click the Payments tab on the left side of the Program registration page:
Then click on any upcoming payment to edit/update it:
This includes applying a credit to it, editing it, and deleting it permanently.