I have two Thank You accounts - one for the Double Cash Card, one for the Premier card. I want to combine the accounts, but when I go to the combine accounts dialog in either account the other account does not show up.

First a rep told me it was because there was a space in my last name in one account but not in the other. I changed the names to precisely match, and now a rep told me the accounts can't be combined but couldn't articulate a reason.

Can these accounts be combined? If so, how do I do it?