The best I can tell you, is that you will have to bring it to a RCA service, AFTER they set up a appointment for you to do so. As they don't do service calls for the "paddle upgrade".
If it is indeed a RCA DTC-100 tuner that's built in, it's then a RCA issue, and not a Toshiba issue.
So what they told you about that, is indeed true.
So I guess your only real hope, is to keep "on" RCA, until they finally agree to do the "paddle upgrade" for you.
And yes, "Lisa" at 1-877-722-4388, is the only one that I'm aware of, that handles all the "paddle upgrades" for RCA/Thomson.
If she can't help or give you more information on what you need to do, I don't really know who can.