handle PI sender binary text

Customer send text file by AS2, but PI can't parse Chinese characters.

I wrote some Java code, find out the text file is GB2312.

I have tried very hard to parse the text file with modules, but failed

AF_Modules/TextCodepageConversionBean

AF_Modules/MessageTransformBean

I convert the file to UTF-8 and PI can parse it.

But the customer don't want to use UTF-8 format.

Do I have to write a module?

thanks