I am working on a learning research project on how toll free numbers work. From my conversations with long distance carriers in the US, they indicated that they charge based on where the call is originated from. When they bill, they would indicate the cost, NPA, NXX, OCN, ....etc
The question I have is how can I derive similar information real time during call setup in SS7? :( not sure which fields and layers I need to look in.
I would really appreciate some help from experts in SS7 out there.