The Billing Page in KnoCommerce identifies the plan the account is on and basic billing options.
Accounts for whom Billing is done through Shopify will have a 'Current Plan -> Login to your Shopify account to view billing info' message. To view billing options for Stripe accounts, check out the billing page on Stripe help doc.
Change Plan - View other plan options and make a switch to a higher- or lower-tiered plan option.
Cancel Subscription - Cancel the billing subscription and downgrade the plan to the KnoCommerce Free plan.
To view billing information beyond the basics shown in your account, you'll need to log in to Shopify.