If you only used one leg of a return ticket, you can ask Trainline for a refund. Their policy says that returns are refundable when both ways are unused or when only the outbound (first leg) was used, so you can get a partial refund.
How to do it: If you want to get your money back, go to "My Bookings" or the confirmation email, hit "Manage Booking," and then "Request refund."
You'll need to check with Trainline to see what kind of return you can get. The amount may be different because they take away the cost of a single ticket from what you paid.
If the problem remains unresolved, consider filing a complaint on Xolvie to raise awareness about the issue and inform others.
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