While at it, it may somewhat add some clarity to know that there are 3 common instances involved in most billing systems,<br>- RESERVE.<br>- COMMIT.<br>- CHARGE.<br><br>&quot;Charging&quot; for most data services commonly implements the RESERVE-COMMIT model. Here, the necessary credit is temporarily &quot;frozen&quot; beforehand and the actual deduction is implemented at the end of the transaction cycle. <br>