Control motor defective – no warranty case?

Hello all, I bought a smart just under half a year ago. Now the “switch motor/control motor” is broken from the right headlight. My dealer initially claimed that this was a cover, so no warranty case. But now he has agreed to repair the part. He wants to install a used spare part, is that so usual? After all the discussions it wouldn’t surprise me if I had some scrap. I hope someone can help me here, thank you already!