Hi Richard,
So it’s been an eventful 7 days!
I agree that it’s unlikely anyone else used your phone. If you feel inclined you might want to check google maps timeline (if you have it activated) as that may indicate where you were at 10:27. Another avenue may be to contact your mobile provider and see if they can assist. If your phone pinged a mast nowhere near Bond Street at that time then it would be pretty conclusive. The other thing to ask TfL is why the charges for the 1st one were not incomplete journeys. That points to something fishy to me.
For the overcharges, I’d be asking my bank anyway, so that it’s logged that you’re actively investigating. They may even agree to refund the amount in the circumstances. TfL should only ever produce one transaction per day per card.