8.5 Credits and billing portal

• SMS/Email credits are bought on this page (dedicated cards) and never expire — they're used after the plan's monthly allowance runs out (chapter 6.3).
• If you have an active subscription, the Manage billing button opens the Stripe portal (payment methods, invoices).
• When switching plans with an active subscription, the unused time is credited to the next invoices (Stripe proration) — the screen explains this before you confirm.