1. You should call USCIS service center to check your case status as bellow:
1-800-375-5283: 1-2-2-6-2-4
Oprator will make a requst to your service center (for exsample TSC or NSC) about your case.
2. You should write the letter to your service center again with your copy of last letter.
3. Try to find a senator to help your case.