Notice period buyout mentioned in clause but not allowed to use

I am on resignation and want to buyout notice period as it is mentioned in my appointment letter but my employer is not allowing me to do. Clause mentioned in my appointment letter: "Notice Period: Either party has the option of terminating the employment agreement by giving the other party a notice in writing. If the employee has been in the employment of the company during first Six (06) months of employment, the notice period will be thirty (30) days and after completion of Six (06) months of probation period and /or for confirmed employee, the notice period will be Sixty (60) days. In case the employee is bound by any undertaking or other similar document at the time of termination of employment by either party, the employee will be liable to compensate to the company for the applicable amount as per the undertaking or other similar document. In case, one party does not agree to waive the notice period then the other party can still terminate the employment agreement by paying money that is equivalent to the basic salary of the employee of thirty (30) / Sixty (60) days of notice period as applicable, along with the amount (to be paid by the employee) under any signed undertaking or other similar document, if applicable. Once the employee tenders his / her resignation and is serving his / her notice period, he/ she would be expected to ensure that the quality of work and client relation among does not suffer. The employee is also expected to extend full co–operation to ensure smooth transition. Any non–compliance with this will be treated as material breach on the part of the employee for which the company may take strict disciplinary action against the defaulting employee."