Problem in dynamic file name in File reciever adapater

I have given my file name as

%abc%.txt

and in the advanced mode

i have given

Additional parameters as

abc=

payload:file_reciever_mt,1,FileNameNode,1,FileName,1

while my file reciver structure is

<?xml version="1.0" encoding="UTF-8"?>

<ns:file_receiver_mt xmlns:ns="urn:filetofiledemo"><recordset><data><name></name><age></age></data></recordset><FileNameNode><FileName>Amit123</FileName></FileNameNode></ns:file_receiver_mt>

My file is getting store as %abc%.txt

not as Amit123.txt

I am using SP 14 .

Any pointers wld be very helpful

Thanks

Amit