Hello Venu,
You can try this.
If Customer local system is on same network as SAP system, then create one folder in customer local system and map that folder in SAP System.
Later include this folder in SAP System directory (TCode: AL11). After you save, try to double click the folder and make sure you are able to open it from SAP GUI.
If above is success, then you can include above AL11 path in your program to save the file.
Hope this helps.
Best Regards,
Srikanth