If you dont want to be a global change then just remove formatService in the particular EDI FFDictionary/Field you will see formatService option(Generally formats functions apply for qty or amount related fields).So dont change the code in the formatService itself.
Note:You have to migrate the existing dictionary/schema changes to different environments QA,prod to sync.
Also you will find all the format related functions located in the packages/WmEDI/pub folder format.xml…
HTH,
RMG
#Integration-Server-and-ESB#webMethods#edi