An issue which caused some customers to be overcharged when using the new Elizabeth Line has been corrected, an online rail and bus ticket firm said.
Trainline said it had identified a problem with the way some fares were being calculated into London stations.
The company said it would be contacting customers who bought the higher-priced tickets "to make sure they do not pay more than they need to".
The issue apparently stemmed from the lack of availability of Bond Street as a destination on Trainline's website and app.
"Our tech team have investigated and deployed a fix that has resolved this issue," the firm told the BBC.
Since 6 November, passengers have been able to travel on the Elizabeth Line from Heathrow, Reading, Abbey Wood and Shenfield across London without having to change stations.