"I changed the design but the phone shows the old one"

First, the reassuring part: the change does reach cards already handed out. You do not need to reissue them.

What confuses people is when it arrives.

A card updates when something happens to it — above all, when you stamp it. If you changed the design a while ago and look at a card nobody has touched since, you will see the old one. That is normal.

How to check it properly: stamp a customer's card (or your own test one) and look at it afterwards. If the new design shows there, it is working.

Careful about testing with your own card: by stamping it to check, you are updating it — so you will always see it looking right. That hides exactly the case you are worried about, which is the card nobody touches again.

On Android it can take longer. Changes go out in batches, not all at once.

If a whole day passes and a freshly stamped card still shows the old design, that is genuinely odd: write to support@hexbites.app telling us which program it is and when you changed it.