My employer agreed to reimburse my COBRA for this month because they did not have their health coverage in place, as was agreed upon. I extended and paid the COBRA upfront and mid-month I was offered a new position and resigned my current position. Now the employer has notified me saying they are rescinding their offer to reimburse my payment because of my resignation. I have emails to show our agreement. Since they agreed to cover these costs because their coverage was not in place, can I sue to get them to reimburse this cost as was initially agreed upon?