Just went through this and the thing that unstuck me was recording the calls with permission and then reading the transcripts instead of my notes. My notes were full of my own words. The transcripts were full of theirs.
I pasted all six into one document and highlighted every phrase that repeated. End of month came up eleven times across four calls and it always had a date attached, the 5th, the 8th. That turned into the whole product, because it meant the tool has to be useful inside a three day window rather than continuously. I would never have got that from my notes, which said wants reporting.