Prefacing that Japan is not open to foreign tourists currently, but this post is for future reference. The coronavirus pandemic affected Japan heavily, like many other regions in the world, but along with it came the rising trend of remote work. In response, several Shinkansen bullet train operators in Japan started providing a remote work train service.
For example, the Tohoku, Joetsu, and Hokuriku Shinkansen trains, which service Kanazawa, Niigata, and the Tohoku region of Japan started an office car service. In the office car, passengers are explicitly allowed to make phone calls and join online meetings from the train, which are activities normally discouraged on trains in general in Japan. There’s no extra charge for this service, you just need to explicitly reserve a special car on the train. You should be able to reserve this with the various JR Passes as well, either the nationwide pass or the JR East Pass. I haven’t ridden this myself, but you can read more details here: https://english.kyodonews.net/news/2021/11/e3350c504173-jr-east-launches-bullet-train-office-cars-amid-telework-demand.html