I bought tickets on Frontier through JustFly. It said that we couldn't make seat assignments, but I was able to pay for a "please seat us together" option. We did this because my husband was afraid that if we didn't, we might get bumped if they oversell the flight and there are very few flights (Frontier or otherwise) going from Denver to Calgary. I just logged into the Frontier website and it looks like I can choose seats there, but of course I would have to pay again. I don't care about where we sit or if we sit together, my main concern is getting bumped and not getting to Calgary that day. Are we at risk of getting bumped if we don't have seat assignments?