Vietnam Air pretty much used to be the only way to go and interestingly, at least from some locations (I think Bangkok, maybe Singapore, I can't recall) they would take CASH only!

The only other time I remember something like this was on Olympic to Athens about 8 years ago. I call- busy, busy, .. connect, wait, wait, ... schedule the flights rt with the agent and then she explains, about one hr later, "we dont take credit cards!" Moreover when I asked if she'll hold the flights for me and I'll pay and pick up at the airport, she says "No we cant do that!" When I asked how we could work it then she says "I dont know! We cant!" Wonder why they have financial problems!