Concept users will be migrated over to the Flex pay as you go plan. Sending will be .80 per 1000 email or 0.0008 cents per if sending is under 1000 emails.
For accounts moving to the new Flex plan on March 1, the first invoice for the new plan will be issued on April 1, as pay-as-you-go plans are post-paid.
Please let us know if you have any additional questions.