after better understanding requirements, seems like company using enswitch with possible API access through SOAP messages. As there's no evidence that SOAP is well implemented, I propose to handle this project by directly interacting with asterisk, and dropping enswitch, especially that client only requires few functions not specific to enswitch, and which can be implemented with asterisk's AGI module and PHP functions to call them, the whole thing delivered as a PHP website, or wordpress plugin for instance.