Principal — mail id is hacked-how to retrieve the account

Address:

ArulmiguPalaniandavar Polytechnic College, Dindigul, Tamil Nadu, 624601

My rediffmail id is hacked and help me to retrieve my account since it is used for office purpose. In my recovery question, my alternate mail id and my phone number have also been changed. also i have given the rediffmail id for my personal use and official use. Further it is being used for research purpose of my area of interest. hence my rediffmail account may be restored