You can easily view how many messages you've used as well as the date of when it will reset. Messages do not roll over from month to month; however, keep in mind that all incoming messages are free. Text In Church only counts outgoing messages towards your allotment.
Under Settings, in the Account Overview tab, you can see how many messages of your plan limit you have used so far, as well as your counter reset date.
The counters reset at midnight UTC time for all accounts on your invoice date or the date listed under the Account Overview tab.
If you need more messages, you can upgrade at any time: Update Your Plan.