Modify xml document options

I need to modify the xml document genereted when invoicing customers. The service

name is: SalesSalesEInvoiceService.Read which is enabled thru AIF. The question is

how can i modify - the XML file that the read operation generates. I want to modify the

itemname from the custTrans table and other fields. I thought it would be possible making changes to

the AXCustInvoiceTrans classes (the parm) methods - but it seems that the service does not

use these classes at all (I dont get into these AX tables when debugging)

Any suggestions ?