Besides FastMail is in Australia, my father is in the UK and I am in Japan ...
Also, would the court order FastMail to continue to offer service to my father, which is what I want. I very much doubt that. FastMail would just be allowed to make the offer of the $15 plus some half-price deal on another plan, which they have done already.
On the other hand, companies do seem to rather dislike bad publicity. So when they try and back-out of past agreements and contacts that no longer suit them, it is far more effective to call them out publicly on forums like this one.