This article explains how you can Edit or Cancel your Client's Active Membership Periods.
How to edit charges and scheduled payments
Go to the Clients tab then select your client to pull up the profile. Next go to the 'Services' tab:
Click the Edit icon of the membership. This will pop up new window that will display your client's membership information. The 'edit' option allows you to modify existing information. And the 'pencil' icon allows you to alter fees per period
Skip charges, scheduled payments and allocated credits:
Hit the 'bin' icon (example below), then you'll have these options to choose from:
Skip membership credits between dates....