If you touch your Oyster card on a yellow card reader when it's in the same wallet or purse as a contactless payment card, the reader may detect more than one card. When this happens, the card reader doesn't know which one to read. This means:
Only touch one card on the reader when touching in and out to avoid paying with a card you did not intend to pay with.
Sign in to your contactless and Oyster account to make sure that the card that you intended to pay with has been charged for the journeys you have made. If you also have a contactless payment card, you should check the journey history on that too, to see if there are any unexpected journeys on that. If you have been charged a maximum fare on two separate cards for the same journey, you can apply for a refund by signing in to your account.
If you have been charged a fare on a card you did not intend to pay with, please contact our Customer Services team on 0343 222 1234 (TfL call charges).