Sorry, but what cmwade mentioned was a special promotion that has since expired.
Instead, near the end of your vacation, sometimes (but not consistently) some (but not all) of the hotel front desks may be willing to convert a few TS credits into CS credits, on a one-for-one basis, no snack coupons, no lanyard, and with the understanding that there is no way to convert the credits back. However, again, this is not an official part of the Dining Plan, just a courtesy that some hotels extend to some of their guests, some of the time... don't count on being able to do it.