I do have the distinct impression that the Can. credit card was important as I was theoretically calling from Canada. They were very clear that they wanted a Can. credit card. Now I can see no way that they can refute you purchasing a ticket in Canada with a US credit card but as I said they are very difficult with this issue and it would be hard to confirm it unless you actually gave it a shot. I felt it was important to have the rules from oneworld that reference this anomaly in front of you everytime you speak to someone. I had to reference it more then a few times.