Thanks Jim
The best way to learn from anything like this is "What did I do wrong so I won't fall for it again? "
I got an email from the hotel telling me that my booking was suspicious. But as it had the correct dates and reservation number, I was not remotely suspicious. I just did not want to lose my booking.
So I followed the instructions.
Lesson 1: Don't be afraid to make a phone call. We get out of the habit of calling service providers and prefer to do everything online. If I had called the hotel, that would have been the end of it.
To verify it, they asked me to pay the amount and then they would refund it. That again was odd but I was not suspicious as it was from the hotel.
So I entered my card details and paid the amount.
Then I got a message saying due to a heavy load it might take a few minutes to process. This is not that odd as I have often made payments, verified them on AIB with my phone, and they say "Don't press the back button or reload..." .
Then I got a message saying "this has not gone through, try again..." So I had put in my details a second time when I thought "That is too many odd things happening..."
So I checked my AIB account and the first payment had gone through. So I didn't proceed with the second payment.
I rang the hotel and the guy didn't speak much English. I said I had got an email about a fake booking and he said "scam".
Lesson 2: If there is a series of odd things, no matter how genuine they are, stop and think.
I then froze my card online.
I called a German friend and she rang the hotel and was told that they were plagued with calls that day from people who had received the email and it was a scam. But my booking was not fake.
I googled it and found that this scam has happened before.
I rang AIB but they said that the payment had been authorised so they could not recall it.