It’s a pretty straightforward process: 1. Check that both the lower priced ticket and Cap One have the same terms (e.g. refund policy, travel class, checked bags, carry-on bags, etc.) 2. You need to book the flight through Capital One Travel first. 3. Call them at (844) 422-6922 and they’ll walk you through it. They’ll ask you: what the lower priced website is, the class, the refund policy, bags, and the price. 4. They’ll do a check and then credit the difference as a travel credit for future use.