@marta Many places may have to go back to that to bypass encryption bans & quasi-bans that exist alongside warantless wiretapping bans.

It should be possible with sound modem software (such as soundmodem, direwolf or linmodem and some configuration or coding depending on which) and a TRRS jack or a splitter to manually establish a call on a cellphone (with the human interface) and then setup a PPP/SLIP (or other) connection.