Curve, the London fintech that lets you consolidate all of your bank cards into a single Curve card and app to make it easier to manage your spending, has added support for Amex cards.
I've been using Curve for a few months to manage all my expenses from multiple accounts with a single card. The app is really easy to use and you can quickly switch from one account to another with a single tap. It would be great if they could improve their support though - I've had some issues with the cashback feature and some refunds that have not been displayed correctly in the app, and their response time is usually longer than a month.
