Fatca notice received under sec 133(6)

I had received a notice by post from Joint Director of Income tax (I&CI) Hyderabad w.r.t a subject of "Information Received under FATCA from U.S." seeking clarification for some money transaction in my U.S bank account.

I responded to this letter twice by Indian post on and before due date that I don't hold any bank account in U.S. and not aware about the transaction mentioned in the notice sent to me.

I again received a FINAL OPPORTUNITY notice recently w.r.t same letter which was originally sent few months back claiming that no response have been send from my side and provide update on or before 13.03.2018.

I am looking for a help on this matter and seeking an opportunity of better communication medium. The issues I am facing are ... 

1. There is no specific address mentioned in the notice where I should send my reply by post. I am sending my responses to Mr. XXX, Additional Director of Income Tax (I&CI), 3rd Floor, Aayakar Bhavan, Basheerbagh, Hyderabad, 500004. This is the only possible address I can figure out in the notice where I can send my response by post but some how this is not reaching to concerned officier.

2. Recent notice, I received on 14.03.2018 which has already passed the set due date 13.03.2018 to respond as final opportunity. 

3. There is no e-mail address where I can send my updates.

4. There is no phone/mobile number where I can reach out to get further clarification. The office number mentioned in the notice 040-23425132 is not getting attended by anyone.

Please guide me how should I proceed further on this matter.