Upgrading applies immediately — the new plan's Credits and kill allowance land right away.
Downgrading or cancelling stops the renewal at the end of your current period. Until then, nothing changes: your balance stays live, renders keep working, your kill allowance stands.
After a cancellation takes effect you lapse to Free — and everything you kept remains yours, commercial use included. Top-up Credits survive the change; only the plan's own monthly Credits expire.
Manage all of this from your account page — no email required, no retention flow.