Did you get it through your phone messages?
Have you ever given TfL your phone number?
If the answer is yes and no, in that order, it's a scam.
I had one a couple of months ago, and my answers to the above questions were yes and no, in that order.
So I thought I'd check with TfL to see how long it would take them to respond.
it took them several days, by which time I could have been scammed for a lot of money.
I replied to them pointing out how bad and slow they were about informing people that the messages were scams.