Just had a Monzo 3D Secure alert for £60 from Crystal Palace Football club on my phone. Was confused because my card has been in my drawer for over a year but confirmed it was definitely a genuine alert and coming from Monzo.
I denied it now CS claim they can’t see it anywhere which is weird.
And they froze my card so I activated my hot spare but can’t see how to go back to the original card in app now.
Once you have activated a card you cant roll back to your previous one. The one you activated is now your card.
So I need to freeze and reorder a new hot spare which I don’t activate.
I’m also confused how someone made this online payment when my card hasn’t left a secure location in my house.
Sadly we can’t clear up that confusion. You know more than we do about the situation so your best bet is to have a chat in app where they can dig a little deeper 
It’s probably someone has got hold of your details from a compromised website, which is weird that they can’t see.
Do let us know what monzo say if they get to the bottom of the notification.
Off topic, but can you let me know how you go about getting a hot spare with my existing card still working, it sounds like a good idea.
Should be impossible to get details and CCV from a website.
Last time I just froze, ordered a replacement then thawed.
Maybe they weren’t using the security code
I know even with wrong details on 3D secure transactions they let it through to the phone to authorise.
But I’m not sure about something as critical as the security code.
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Thanks ordered a spare, will be great to have as a backup abroad.
Pretty much the only way I use Monzo these days which is why it’s more confusing how my card was compromised.
Get monzo to dig into the logs, maybe it was from someone else’s account👀
Amazing. Monzo chat now blocked the wrong card (my hot spare) without my permission and I can’t unfreeze it.
Uh oh, good luck.
Fingers crossed someone competent will be on shift before the morning.