Notice Period Issue

I have joined IT organization four months ago in July. I want to resign from the organisation at the earliest due to personal reasons but HR and manager is insisting to serve notice period of 3 months. I have offered for replacement as well as buy out of notice period.But thy are denying to accept it and harassing me mentally. The terms of termination mentioned in my appointment letter are as follows: 1) During the period of training, LTI alone has the right to terminate the contract of employment by giving one month's notice to that effect in writing or basic salary in lieu thereof 2) After completion of the said training and confirmation thereof, LTI has the right to terminate the contract of employment by giving three month's notice to that effect in writing or basic salary in lieu thereof. 3) The right to terminate the contract of employment can be exercised by you upon giving at least three month's notice to that effect in writing. Wat should i do