What's up Take?
So calling Japan is really the only problem. I recall helping another customer with this some years ago, and he/she was having trouble calling China if memory serves correctly. Thank you for telling us that calling Japan is the only real issue. That tells us a ton! You probablywon't need a tech visit.
Spectrum chat is not all that great for problem solving. This is something that is affecting you directly. I would recommend sending a Direct Message to our excellent Moderator Staff at our forums. Do that by sending a Private Message (PM) to this link
They MIGHT still want to send out a tech, but I would doubt it as calling Japan is the only problem with your Spectrum Voice (phone service.) I would follow through with their recommendation. In the meantime, allow about 10- 14 business days for this issue to be investigated. This is a process that's going to take some time most likely, because it's isolated to one problem with a specific service, related to one country. It could be the same thing as the excellent example that you gave above, or the same issue some years ago with the customer whom I helped who's calls to China were wonky, but everything else worked. Spectrum may need to research any individual carriers that they use to provide international calls to Japan just to see if others are having that same issue. Some people may not report this because they think, "So far away, international long distance, I am going to have a problem from time to time." But this IS fixable. Contact our mod team at the forums to begin the investigation. You can certainly refer to this specific thread.
Satch