It was a bit disconcerting to her, but hopefully she'd get it resolved because...
Wait, hold on. Danger, Will Robinson. Danger. Stop, do not pass go. Red alert!
I am absolutely positive that this was a scam. One I'd never heard before. And a very clever one. And the more we discussed it, the more she was sure, too. And her concern about a frozen account disappeared.
Why was I so sure?
The first clue was that she was surprised that particular account was frozen. The reason she didn't know the card number was because not only was it a card she almost never used, but she used it so rarely that she didn't even have it with her.
Then there was the oddity of being called on her mobile phone. Why not her home phone, which was the number registered with the account?
And perhaps most notable is that the message didn't say, "Your account ending in XXXX," which is what companies usually say, but just generically, "Your Mastercard account" has been frozen. And then she had to provide the number by punching it in. I am sure that the next question would have been to punch in the 3-digit code on the back of the card.
As I said, I am sure this was a scam. After all, among other things, it seems pretty clear why this came over her mobile phone rather than home phone -- on a mobile phone with a text message, you can immediately punch in your card number. But if she had any doubt or concern, I told her to call Mastercard directly herself and ask if there was any hold on her account.
But I don't think there's any need for that.
I've heard of similar scams through email, but I think this has to be looked at as a different kind of fish. That's because people tend to be at least somewhat skeptical with emails today. But I think they're more trusting with their phone, and calls. So, add a devious scam to be aware of.
And now you are...