Switch jobs post I 140, old employer charging complete GC fees

[MrDV]

I switched jobs post my I-140 (EB3) approval, I had initially signed an agreement with my old employer that once my immigrant VISA is approved and if I leave the company before xx months they will charge me the complete GC fees, the important point here is the agreement said "once the immigrant VISA is approved", but now I have switched jobs post I-140 approval and in the final settlement the old employer has charged me the complete GC fees.

My questions:

• Is it legal on the part of the employer to charge me the complete GC fees
  
• Isn't the I-140 the property of the employer and they should bear the cost for Perm and I-140
  
• If the employer is doing this illegally can I take any legal action
  

Please help