Reza:

There is no problem with making your program answer a modem call and handling all digital traffic. But the audio response part is a different beast and I'm not much help there -- sorry. The best I can recall, from about 12 years ago, was some hardware/software made by an company in Southern California that handled the keypad and voice communications. A VFP (or any other language) program could interface with their package.

One type of application they aimed at was traveling salesman entering orders and making inquiries over the telephone. By now a lot of that stuff has been replaced by the internet.

Sorry I can't be more helpful,

Scott