Today l use my revolut card 's contactless on London bus, usually the bus fare for contactless card is 1.5 pound！！but the revolut system charge me 10 pound！what happen to the system？ and l wish to get 8.5 pounds refund！
See notes here on using TfL.
The difference will be refunded shortly, in my experience it is usually corrected within 24hrs
Hope this helps
prepaid cards arent the best option for TfL