Harassed by recovery agent of ICICI Bank

I am constantly getting calls and the person stating himself as an employee of ICICI Bank and threaten me to pay the dues of outstanding loan. The person has called numerous calls to my family members as well as to my known peoples, perhaps getting nos. from my call data record obtained illegally from the service provider. He used abusive and harsh language and defaming me in the society. Now he has phoned to my boss and used filthy language. He also made a call at my boss' residence and again used harsh language to his wife in resulting I got fired from the job. The so called loan was taken in the year 2006 and continued paying EMIs till 2008 and due to some unavoidable cicumstances I could not pay after that. While obtaining loan papers the banker took two blank cheques from me at that time. I want to know whether the bank can use this cheques against me or not, I am under great pressure for the last six months as they call me any time and use abusive language. I complained to bank but their reply astonished me. They said these calls are for reminders for your loan. They are totally silent on the agents behavior as they are verbally permitted to do such nusience I have stopped picking any call from unidentified numbers. Please help me out of this problem.