FTP Get from GXS VAN via SAP PI 7.1

Hi, I have a requirement of connecting to GXS VAN via SAP PI.  I have setup a FTP Sender Adapter with the server, credentials and file access parameters but I'm encountering an error.  I think the issue is with the 

Source Directory      : %%

FileName                 : %F159B%

Error:

Could not process due to error: com.sap.aii.adapter.file.ftp.FTPEx: 550 Unexpected reply codeRequested action not taken. Extraction command SNRF: 14092314246AIM. TIP error: GOFILE - invalid service reference (must be an 18-digit number).(0060)

Please note that I've been thru a lot of forums already but it seems that almost all are pertaining to FTP Receiver Adapter and this is not a network issue since I am able to ping the target server from PI server.

Also, using Seeburger adapter is NOT an option for me since it will require additional cost, AND creating a local script is not permitted.

Thank you in advance.