You must be talking about SMS, or 'texting'. The way I understand it, non-SMS messaging services use data, and do not show up in your carrier's billing or usage other than to show that data was used, but not the content or in what manner data was used. As far as content of SMS messages, its my understanding that the content of those messages is only available through a court order that is difficult to obtain. That information is not available even to the owner of the account.
FB Messenger and BBM I know do not show up in carrier billing or usage information.
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