“Then I am sure you can name at least one case.”
Of course I can (cancelling of fixed lines despite having contracts), but I won’t, because I want to keep my job there.
But the cancelling of ISDN lines despite contracts was nation-wide, so pick up your random customer, because all customers were affected without exemption. And with ISDN, they did it twice!
The latest cancellation was in 2018 when Telekom abolished ISDN altogether, but they did the same thing before, in the Nineties.
Telekom built ISDN exchanges (PBX) for large customers using a national-only ISDN standard. At that time, I worked for a different company. They trusted Telekom and spent some million Marks for a national ISDN PBX (1TR6 standard).
Much to the surprise of my employer, only a couple of years after that, Telekom announced the abolition of 1TR6 and declared, that the hugely expensive PBX they sold my employer could NOT be upgraded to the new European ISDN (DSS1) and declared that a completely new PBX must be purchased and installed and the “old” one would be disconnected from the network because of “incompatibility”.
My employer sued, and before a ruling in court was issued, Telekom gave in and built a new PBX at a non-disclosed, but said to be enormous rebate. And not only the PBX had to be exchanged, also several hundred (!) telephones had to be exchanged, too.