My cell phones did work in Alaska
Just got back from a 4 month trip to Alaska and back and my cell phones worked perfectly in Alaska, as long as there was coverage.
Many places, even along the Alaska Highway don't have cell phone coverage, due to the distance between towers and major cities.
We did hear that the charges for using cell phones in Canada were extremely high, so we didn't even try. We had an IPAD with us and used it when Wi-Fi was available to send messages and e-mails. Libraries, most visitor centers and many restaurants have Wi-Fi available.
Old Cell phones do work in Alaska!