Q: I recently booked two train tickets from Seville, Spain, to Madrid from Trainline, a ticket reseller. The tickets are 70% refundable.

I needed to change to an earlier train but couldn't do it online. So I purchased two new tickets for travel and have sought a refund for the tickets I couldn't use. I tried to talk to customer service first in Seville and then Madrid. A representative told me to submit my request online. I followed all the instructions on the site.

Trainline has suggested that I'm entitled to a refund. But now, it's saying the exchange is impossible unless I send a screenshot of the error message I received, with a time stamp, when trying to cancel my ticket. Can you help me?

A: Trainline's tickets are refundable, but like airlines, you have to cancel before the train leaves. Trainline says it has no record of you trying to cancel, so it is going to keep all your money.

But here's the problem: Although Trainline said it can process a ticket change request through its site, you couldn't do it. This is a common problem with travel companies. They direct you to their websites for the "best" customer service, but then offer you nothing but dead ends and error messages.

If I didn't know any better, I'd say companies create sites to turn people away — and allow them to keep your money. But in this case, it was probably an issue with your browser accessing a European site or something benign. Sometimes, these things just happen.

Trainline's terms and conditions, which you can find on its site at thetrainline.com, are clear about the timeline for canceling your tickets. I think if you had something in writing that shows you tried to cancel your tickets on time, you could have received the 70% refund. But you didn't have any proof, which made your case more complicated. The next time you have to cancel something before your departure or stay, please make sure you have something — an e-mail, a printout, a cancellation number — that shows you contacted the company before your deadline for a refund.

I reached out to Trainline on your behalf. It reviewed your records and verified that it denied your refund because you had not canceled your tickets through your Trainline account. "She contacted us so we can help her get a refund of these two tickets since she did not manage to exchange them at the station," a representative said.

Trainline says it decided to make "an exceptional refund" and has honored the 70% refund.

Christopher Elliott is the founder of Elliott Advocacy, a nonprofit consumer organization. Contact him at elliott.org/help or chris@elliott.org.