Advice required for billing system for sms messages

We need advice for setting up a billing system for sms messages. The advice is mainly about how to develop a web application that will send sms messages depending on criteria that the customer has entered in their profile. We need advice on how to use some of the criteria the customers have entered and send hundreds or thousands of sms messages to customers and bill them in the quickest way. The issues to be addressed are how to update the database as quickly as possible, should the sent sms messages be saved in a table immediately and then a seperate script be run later in the background to update the customer accounts rather than looping through each customer while the administrator is carrying out the task. If anybody has done this type of thing before we are happy to pay for a couple of hours advice to help plan this task including templates for the layout of the ledger table if you have one. Please only apply if you are a rated GAF member and use the phrase sms billing in your answer. It doesn't really matter about the programming language or database, it is the logic that we are interested in.