I recently got engaged and am wanting to get out of PMC work for my personal safety and for the emotional security of my soon to be wife, so I signed on as an armed guard for a local security company; During the hiring process I told them that I still have one contract left in Northern Iraq on the 27th of February. They said it would be no problem and just to inform my direct supervisor and operations manager. This was in November. I have at the beginning of every month since then reminded my supervisor and operations manager that I am leaving the 27th for my last contract after which I'll be coming back to the company. Today I received a phone call from HR telling me that if I leave the country the 27th for my contracted rotation that I will forfeit all benefits of employment (which aren't the best but they cover my sister's meds and check ups) and my employment would be terminated. I told them that I was informed that this wouldn't be an issue when hired and that it was reaffirmed monthly leading up to it. They are stating now that since my operations manager is changing this weekend that any agreements made need to be renegotiated and that due to labour shortages they cannot agree to my leave status. I have it in writing that they already agreed to this leave of absence and that they already affirmed I wouldn't loose my benefits but they are saying still despite this that I will be terminated and my benefits lost if I go through with this rotation. I'm at a loss for what to do except just take the termination but that puts my sister in a difficult spot medically as a result of an accident at her workplace a year ago.
Edit: Is there any federal laws that might would prevent them from going through with my termination for a pre-approved leave?