changing job after perm is approved

[gsaneja]

I have 6 months left on my h1b visa (6 years completion/usage ends on April 30th). my perm just got approved and to my employer is asking for 7k to continue the green card process and file for i-140;

 

if i get another job and my new employer is ready to file my perm, then could I get 1 year extensions post April 2016 with "new" employer based on my current perm approval with "existing" employer provided my existing employer does not withdraw my approved perm?

 

I work in Finance for a fortune 500 company and didn't expect my employer to ask for money for my green card.