DDO Store not letting me change CC

[Zion_Halcyon]

Keeps telling me service not available.

****ed because it means I can't buy the memorial day points

[Calebro]

Keeps telling me service not available.

****ed because it means I can't buy the memorial day points

Are you using a 1-shot card, like a Tax Return or something?
If so, these types of cards can't be used for anything that has an ongoing payment. They simply won't pass the check, as they don't refill on their own.