(facepalm)
Why on earth would you call Chase?
There are plenty of good reasons why you should NOT call them:
1. They may conclude you have been violating the terms of your CC agreement, close all your accounts, claw back your points, and blacklist you - and they would be both correct in their conclusion and entirely justified in doing so. You're basically calling them and waving a red flag saying "nyah nyah, come and get me!". Don't be surprised if they do.
2. This brings yet more Chase eyeballs scrutinizing purchases at office supply stores. Everyone with an Ink card thanks you for that, Einstein.
3. Most of all, this is an abuse of the "dispute" process. You went to a store and you bought something. By disputing the charges, you are in effect saying "they didn't sell me what I tried to buy". Wrong - they most certainly did. You bought gift cards, they sold you gift cards. End of Chase's part in the transaction. Your dispute is not with Chase (at least until they decide to fire you as a customer). Your dispute is with the bank that issued the gift card that had fraudulent charges on it.
You deal with them, not Chase.
MS has risks. This is one of them (getting all your Chase accounts closed is another).
If you can't afford to float the money, you should find another hobby.