Survivorship bias and the calls that never showed up

You will never know which customers gave up before voicemail. You can estimate it.

The carrier log shows calls that connected. It does not show the customer who started dialing your number, saw the four-star review mentioning "could not reach them," and dialed the next shop instead. That second-order loss is invisible. The proxy is your call volume on days when reviews are fresh vs days when reviews are stale.