No problem! 

You can Pause your billing at any time without losing any of your groups, members or messages. Your billing will be Paused on your next billing date. After that date you will not be able to send any messages till you un-pause your account.  

When you need to use CallingPost again, simply log in and Un-pause your billing. You will be billed right away when you Un-pause your account and you will be able to send messages right away.

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