Employer not accepting resgination

I have a bond with my employer for 4 years. The company is not accepting and not relieving from the company. Below is one point coming on legal notice by my employer to me:- WHat can i do I, therefore, finally call upon you to withdraw unconditionally your Resignation Letter and intimate my client in writing as to when you would proceed on business visa to VTC-USA for six weeks, within three working days from the date of receipt of this notice, failing which it shall be presumed that you are not interested to remain on the rolls of my client. This would be resulting in your intentionally, deliberately and willfully violating the terms and conditions of the Financial Assistance Agreement cum Training Bond in terms of your Appointment letter leading to breech of Agreement. Please take notice that in such event your employment with my client would cease to exist and you will not be allowed to enter the office premises of my client and hence in such circumstances my client calls upon you to make the aforesaid payment of Rs.6,00,000/- (Rupees six lac only) together with interest at the rate of 15% per annum as per Agreement within thirty days from the receipt of this notice, failing which my client shall be constrained to take appropriate legal action against you both civil and criminal including for recovery of the said amount in the competent court of law at your costs and consequences which please note.