So people DO still use it. Just not for ISDA Master Agreements. But actually what an awesome plot point for a novel.

The JC’s guide to electronic communication
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A Teleprinter exchange is the original form of data transmission, developed during the Second World War and used as a secure and reliable long distance communication.
Unlike fax or email, telex has full “legal document status” in every country of the world. It carries proof of RECEIPT as well as proof of sending due to its unique electronic handshake on each message. It remains a reliable communication tool with specific needs in Banking, Aviation and Maritime, and is still widely used in many secure environments including Embassies, Governments, Post Offices and Military organisations worldwide.

The internet was based on many original telex functionalities for direct Inter-Country communication, desktop messaging and the Internet Chat type facility is the traditional telex “conversational” call.

For legally secure, guaranteed transmission, the telex service remains unique, from the transmission of banking “TT” (standing for telex transfer) to Maritime emergency calls, ships in distress, pirate threat to lifeboat launch, it is truly a mission critical communication platform.

See also