You have unlimited messaging during your free trial. No matter how many messages you process during the trial, you will not be charged any fees for them, and service will not halt.
The message counter is only there to show you how well your usage matches your current plan. Since the free trial defaults to our Standard plan, you will generally see a "limit" of 200 messages. However, there are no issues at all if you go over this limit during your free trial.
For more info and instructions on changing your plan, please see our account management instructions.
If you use Onsite Support and your account is currently in trial, please contact us to have your special Onsite plan activated.