You could say “I’m helping a national research project on municipal banking.” Don’t lie, but if they ask directly, you can tell them you’re a volunteer with the Defund DAPL Coalition and/or Greenpeace depending on where you first heard about this.
You can view the research results spreadsheet here: https://docs.google.com/spreadsheets/d/1yLf1rqnHGq7BKvfV45iRrfxEp3DaNCW20qmYqEzPxfY/
You can add your results by filling out THIS FORM. Please fill out one form per city/county you call so the data shows up correctly in the spreadsheet.
If you're ok with getting a call back you can definitely leave a message. If they don't call you back in 24 hours you can call again. Here's a sample script:
"Hi my name is _____, I'm doing a research project on municipal banking. I wanted to know what bank CITY NAME has depository services or payroll services with. You can reach me at NUMBER, EMAIL, thanks for your help!"