Sounds like they should have communicated these changes to their customers. If the customer is not breaking the TOS and you cut them off with no notice because you want to change your TOS going forward that's a bad look.
Most TOSes contain both a provision that they can be changed at any time and that you can be cut off for any reason (so long as it's not an illegal one) and for no reason at all.
Not saying that it's right that they do, just saying that they do.
A quick google in German turns up a legal site that says a contract for ongoing services can't be altered unless there is a clause and they must be notified. I can confirm people were not notified as I'm a customer.
A translation
> In the case of current contracts (so-called "continuing obligations"), e. B. Rental contracts, be it for apartments, web servers, software or the use of a social network, GTC may not be changed during the term.
> In the case of continuing obligations, the contractual partners can either voluntarily agree to the new terms and conditions. However, it is also possible to include an amendment clause that allows tacit change. Then the contracting parties must be informed of the changes and that the changes will come into force if they do not contradict them.
Germany has pretty strict laws about Terms and Conditions since they assume no one reads the things anyways or are able to properly understand them if they did.
