The person buys said product - the code is generated (dynamically with php) at purchase and presented on the success page (as well as email/file download)
The person calls the phone number, and is asked to verify their code via automated system - once verified, the call is routed.
This generated code needs to be stored in a database table for validation. When they key in their code to the phone system, it will look this up.
Nobody answers a phone until it is checked as valid. A call is not routed if the code is not valid.
Not sure if there is any more detail I can provide that will be useful.
Basically, it is an "extended support by phone" product.
Note: The phone system is already setup and working. Just need to add this special product type to osCommerce. Looking for tips on where to start.