Welcome to Norway Shutdown... As this was only introduced yesterday there’s a bit of panic about, and a lot of public information lines are very busy. You could keep trying, but unless you get through to a human I would prepare yourself to cancel the trip. The way I understand things (and I might be wrong) they will either deny you boarding in London or get turned back in Oslo. I would not take a chance they’ll allow you to pick up your bags and proceed upstairs to check in.