VCDS – Suspicion of key copy – What to do?

Hi, if I suspect someone has copied my Keyless Go key, how can I make sure that my car forgets the code from the other key? Is that done with me learning the key I already own? Details, if necessary / Story: My car knows the remote control. So the code of remote control is stored in the ECU or somewhere. This code was copied illegally from the remote control. As I read here in the forum, I can Relearn the remote control with VCDS. But isn’t that the same code again? Don’t I need a new remote control?