Q: A reader wrote in about a trip he is taking in 2010 and wants to use a combination of cash and WorldPerks miles to upgrade his flights. He sent a few emails to Northwest Airlines — a frustrating experience which answered some but not all of his questions. He wants to know what the best way is to talk to an actual person about his options.

A: The best way to get customized service for any WorldPerks reservation is to call a WorldPerks agent at 1-800-44-PERKS. These agents really know their stuff and will spend as much time as is needed searching for the right option. Booking a ticket through a WorldPerks agent costs $20 per roundtrip ticket. You can also go to the airport and book through a WorldPerks agent in person, but that will cost $45 per ticket. Booking online is free, so you could potentially talk to an agent in person or over the phone, get the information, and then try to book online. In our experience, that option doesn’t always work. So if you can swing the $20 fee, that’s probably the best option.