Cancel your plan
Go to Settings → Manage billing and cancel there. You don't need to email anyone. Your plan stays active until the end of the period you've paid for.
When the plan ends, your monthly plan credits go to zero. Top-up credits stay on your account.
Failed generations are refunded automatically
Credits are reserved when a generation starts. If it fails, is stopped, or is blocked by the safety check, the reserved credits are returned to your balance automatically. You don't need to ask.
Refunds of payments
Unless the law requires otherwise, payments aren't refundable once credits or services have been used. See the Terms of Service. If something went wrong with a charge, contact us and we'll look into it.