<?xml version="1.0" encoding="UTF-8" standalone="no"?> <Result> <id/> <success>false</success> <errors> <error> <statusCode>USER_ERROR</statusCode> <message>Items on this line have been fulfilled. If you wish to delete the line, you must first delete the corresponding line(s) in the associated transaction(s).</message> <type>ERROR</type> </error> </errors> </Result> we are trying to update 1 field,may i know what is this error