If you would like to have an impact then state politely that your dad needs help with their software tell them he is advanced in age and the local elders are not helping him sorting out the issue and since you are no longer in the 0rg you cannot help with their software. Could they provide you with the name and address of the CO or could they forward your letter to him?
Tie them up in requests. Keep writing them every couple of weeks or a month, asking for them to sort it out and fix their problem since they made your dad buy the device.
Ask them what or who you need to contact to get your father the help he needs as a publisher.
Don't accept their solutions but come up with a follow up request that they do something. Becoming a pain in their butt will get you more satisfaction than venting your frustration with a letter they will just tag as written by an apostate.
Keep demanding they do something and be like the widow asking the judge for justice. But be polite and be persistent.