What happens if a user goes over the send limit on a basic monthly plan?

A user will be prompted to increase their monthly sending limit by paying the difference between the current pricing tier and the higher tier. A user's options will be:

• Hold off on sending the campaign until the next billing period starts.
• Pay the difference and send immediately. On the user's next billing cycle, their sending limit will return to what it was and they'll be charged the normal monthly fee.