Paid plans are billed through our payment processor, at the price and billing period shown when you subscribe. Moving from Starter to Growth is done at checkout from Settings, Plan & billing, and a redeemed code raises the workspace to the plan and seats it grants (it never lowers either). Once your workspace pays by card, updating the card, seeing invoices and cancelling happen in that processor's portal, from the same page. Changing the seat count or any other plan change, and everything for a workspace that does not pay by card, is done by writing to us at billing@workwrk.com.
If a payment fails, our payment processor tries it again. If the subscription still ends unpaid, the workspace moves back to the free Starter plan and keeps its people and its data: nothing is deleted because a payment failed. Section 9 says what happens to the data when a workspace is deleted.