For your calls to the USA, purchase prepaid telephone cards. By using these cards you can call Norway-USA for about 10 cents a minute. Telephone bills that you receive in the USA show all the detail supporting the monthly charges. When you receive your monthly invoice in Norway, just accept the bill and forget about getting a listing of all the calls made and the corresponding rates. There is apparently some secret formula used to calculate the phone charges and the telephone bureaucracy can not remember where the formula is filed.
Public transportation is excellent throughout Norway.
In Trondheim, I suggest you invest in good Gore-Tex walking boots and parka for the winter months. Your children will need rain outfits. Buy the weather gear in the USA and bring it with you. It is more expensive when purchased in Norway. If you absolutely must have a car, be prepared for gasoline prices of 10 NOK per liter.