I'd love to keep more phone calls in my log. Ideally the past month (if possible). But I don't see any way to change this. Is it possible?

The phone call log is NOT automatically deleted, like email, after a certain amount of time passes. Try Messages > View Folder > Phone Call Log. How far back does your log go? You may have to change the default display options. Phone > Options > General Options > Phone List View > modify to desired view.

Many thanks, Doug!