How do I change Payment Plan text on the Cart page?
If you want to change text that the plugin displays on the Cart page, such as "Payment Plan: Pay Monthly" (and are comfortable with WooCommerce programming), you can use the gettext filter.
For reference, you can check out woocommerce-payment-plans-for-subscriptions/admin/class-wc-payment-plans-admin.php and see how we've changed "Subscriptions" to "Payment Plans." This is done at the current_screen action, which sets two filters: gettext and gettext_with_context. You only need to set gettext.
Note: We cannot provide support for any custom programming that you perform related to the plugin.