Long distance calling used to be a pretty big deal. Even intrastate calls outside of your local calling area could be expensive--in fact, sometimes more than interstate. For BBSs, there was various software available that basically let you logon, do your uploads and downloads of messages, hang up and do your reading and writing offline.
Go back a few years further and people would do all kinds of tricks if, for example, they just wanted to signal someone that they'd arrived somewhere safely. They'd make an operator-assisted person-to-person and the receiving caller would just say that person wasn't there and there would be no charge.