Can I retain my I-140 dates from my old application even after it is revoked by my old employer?

3 yrs back my old employer filed my GC, My labor got approved but my I-140 go rejected because my employer failed to show enough financial support/ Lack of funding. So he refiled it again. Meanwhile, I consulted many friends and lawyers and all suggested me to switch the company as I was in my 5th yr of H-1b. Therefore, I changed the company about 6-7 months back. Yesterday, my ex-employer called me and told me that my I-140 got approved and he want me to join back his company other wise he will revoke/withdraw my 1-140. Can he do that?? (I am doing similar job/in-fact with same client company on same position) I don't want him to treat me like this. Please Guide. Thanks for your time.