In pre-internet days they were remarkable aids to business. I remember picking up my Minitel at the Telkom store in Randburg Mall.
As a dealer in property I was given access to the Government portal and could investigate and review the Deeds Office transactions and archives.
I seem to remember it came along in the mid '80's, certainly by 1988 I was into an IBM PC with 44Mb hard drive and 640Kb RAM yeah!!
SA Telkom probably got the Minitel at a sell off price as a thank you for SA Defence Force buying more Mirages, but I'm just being cynical.