I have changed the headers to:
The problem description now:
Whether you send any file above 5Kb or 7 contacts, (I have not tested below this and except 1 contacts);
Whatever request it is (we have registration API available to test in and we have tested in it).
The Time-Out Error comes exactly at 3.07 minutes.
The response is never reached neither 200 Ok_ready_to_receive_the_response section.
I think now sombody can help up getting this clear picture