If a customer requests cancellation of their preapproved payment plan go to:
Sellers > Reports > Preapprovals or click here.
You can search the keyword by entering the customer email in the keyword field.
Once you have located the preapproval you want to cancel click on Details > Cancel future payments.
If a preapproved payment plan is cancelled and the customer wishes to reactivate it, they will need to purchase the product again. There is no way to reactivate or make changes to a cancelled preapproval.