Suna,
Here is a link to NI Developer Zone examples showing how to use the serial port on an FP-20XX module to control a modem and do file transfers. It includes the LabVIEW code for both the PC and the FP-20XX.
http://zone.ni.com/devzone/conceptd.nsf/webmain/4B5DC1F4481A33F286256B4A007D0216?OpenDocument
Regards,
Aaron
LabVIEW Champion, CLA, CPI