If your Qonto card has been stolen, log into your account and go to your 'Cards' section. Select the stolen card and click on 'Block card' in the lower-right corner.
Then select 'This card has been stolen' and enter your password. Please be aware that this is an irreversible action that will definitively block your card.
We also urge you to check your recent operations to make sure that there has been no fraudulent use of your card. If you have any doubt about a transaction, please report it.