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In addition to its own products, our client operated a post-paid Global Calling Card service on behalf of Cable and Wireless. (Calling cards have largely been resigned to history; they were a mechanism whereby you could reduce telephone costs by placing a local or free call into a third-party telephone company's infrastructure, and from there connect to your ultimate destination, thereby bypassing your own telephone company if their charges for the same call would have been higher. You would then receive a monthly invoice for those calls made via the third party.)
Complete Codesmiths architected, designed and built the payments and collection system associated with the calling card service offered by Cable and Wireless, using a combination of Visual Basic 6.0 and SQL Server 6.5 and 7.0.
The billing and collection ‘engine’ consisted of hundreds of tables managed by a large series of stored procedures with some triggers. External interfaces were coded to communicate with the telecomms equipment (to retrieve calls details), BACS, the major credit card companies and the company’s accounting package (Sun). Access to the database was provided for using Visual Basic objects within Microsoft Transaction Server and Visual Basic front-ends, although Complete Codesmiths was not responsible for the front-end application itself.
One unusual feature of the design was the use of triggers to ensure the integrity of discount and promotion plans. Typically triggers are used to provide an audit trail, to calculate data, or to enforce complex data integrity rules. In this case, they were used to ensure that the rules for the various time-based discounts - which were stored in the database - could not be altered once the validity period of the commenced. For example, if the calling card was offering a 15% discount on calls between the UK and the Republic of Liberia duing the month of August for customers who met some eligibility rules, then those elibility rules could not be changed after 31st July and triggers would reject any attempt to edit the details of the discount after that date.
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