Unpublishing a plan doesn't turn off auto recurring payments nor does it disable their existing subscriptions. You need to disable those yourself or let users cancel their subscriptions properly. Unpublished plans just disables access to the plan for new purchases.

Ideally in the future we'll use token based payments for recurring payments and entirely handling the scheduling on our end instead of relying on a payment processor having recurring payments notify us. This would allow things like unpublishing to turn off recurring payments cleanly as we'd just remove them from the recurring scheduler.