I travelled on the Underground from Kings Cross to Heathrow on Friday 28/7/17 at about 1.00 pm. I used my contactless card, TfL have taken £3.10. Returned on Saturday 12/8 and travelled in the opposite direction at about 8.00 pm. TfL have taken two payments of £3.10 for this journey. Have I been over or under charged, if over how do I get my £3.10 back?