Ask every caller where they are driving from, and write the answer down
Origin is the single most predictive field you are probably not capturing, and it costs one sentence to collect.
Front desks ask for a name, a phone number and an insurance carrier. Almost none ask where the caller is coming from, which means nobody can later explain why show rates differ between two campaigns that looked identical.
Add the question to the script early and naturally. It helps the caller too, because it lets your team offer the office that is actually closer and warn them about the drive honestly rather than discovering it later.
Store it as a field, not as a note. A ZIP code in a structured field can be reported on. The same information typed into a free-text comment might as well not exist.
Within a couple of months you will have something useful: booking and show rates by origin. Practices are routinely surprised by which areas produce patients who come back and which produce a single visit.