Change job, But the old company refuses to give me copies of m

I am EB2. LC and 140 were approved and I485 has been waitting for more than 7 monthes.

Right now, I am about to change job to a new company. According to AC21, I am allowed to change job. However, for some reasons, my old company does not want to give me a copy of my approved LC and 140. They said the LC and 140 belong to the company so they have the right not to give me a copy.

Is this true? What should I do in this case? Can I still change my job if my old company refuse to provide me the LC and 140 copies?

Thank