Yes, I think you can.
I got Black on a free promo - it would never have been worth paying for it for me.
Basically, I get almost nothing in rewards, because they don’t cover the places I shop, so Black without any fee-free Amex has no real benefits for me. I’m not keen on the topup system they’ve implemented anyway…
All in, it just made more sense to switch to Blue and continue using its core benefit - lots of my cards in one place. It seemed like the easiest way to get off the insurance quickly too.
Plus the total fiasco this week has made me very circumspect about Curve altogether. The communication and delivery have always been a bit scratchy in places, but this is a whole new level.