You should be able to downgrade your Explorer credit card to the Travel Bank credit card. For that, you should contact Chase or United to know the details. Just remember that when you downgrade, you will lose all the perks that are offered with the Explorer card. Also, since you do not fly United often, the Travel Bank credit card may not be the best option for you as it earns 1.5% TravelBank cash back on everyday purchases and that cash back is redeemable for United travel only. A better option for you may be a regular travel rewards credit card that will reward you for all purchases with at least 1.5% cash back. And regular cards allow redeeming for travel statement credits and cash. That means, you won’t be tied to one particular airline, but will be able to redeem with any airline or for non-travel purchases.