I'm connecting my customer (a 100-employees company in Switzerland) to one of the major service providers with a SIP trunk (this trunk would be the primary way to PSTN).
The SP puts forward a number of requirements, such as national/international context in To: field, then some special requirements for CallerID privacy, etc. The problem is, we can't get a document that describes the technical details of the interface, and SP refuses to create such a document. All we've got is a number of emails and some information from phone conversations. Also an example for a Cisco CUBE router and a Visio drawing with some IP addressing information.
Is it a common situation for such a service? Am I too naive with my expectations to receive a fully documented service? If it were a no-name lousy cheap service provider, I wouldn't ask :)