I did that, too, via dial-up. I used the most
excellent Pro-YAM
terminal software on my PC to answer.
Too bad the author was such a tool about the protocol.
I remember that he went out of his way to ensure that no
other terminal program could speak zmodem with the
freely available versions of DSZ or the Unix and VMS
zmodem programs.
In particular, he threatened the author of TE/2, a terminal
program for OS/2 ca. 1990, with respect to that issue.