How can I change the attachment filename of an EFT remittance file?

We are running GP2015 and using EFT.  We now want to email the remittance forms.  We have it working in our test environment but the attachment filename is in the format "companyName"_EFT00000000123.pdf.  I would like to replace the companyName prefix with a fixed value; e.g. ABCD_EFT0000000123.pdf.

I've Googled my '$#%" off and haven't found anything on this topic.  Does anyone know if this is possible, and if so, where I go in GP to establish the filename for an EFT remittance?