Dear Aziz,
Like in aesthetics, beauty is in the beholder's eye, in employment, ethics is in the contracting party's attitude.
When you are required by the prospective employer to disclose the details of your previous employment, it is your duty to disclose them as they were and not according to your discretion for whatever reasons.
Similarly, when the particulars of previous employment furnished by a new employee is not concocted but only incomplete, the employer can view it as a mere omission in the nature of non-compliance but not as a lack of ethics resulting in independebility so as to warrant the extreme punishment of termination with stigma. And the employer's refusal to give experience certificate is like adding insult to injury. But one should remember always that in a contract of employment, unfortunately, the employer is a superior party and particularly the employee has to be beware of this in his transactions both pre-employment and post-employment.
Therefore, in my considered opinion, only two options are before you:-
One is seeking an audience with the CEO and requesting lenience as the omission was purely unintentional and continue your services or to permit you to resign gracefully with a service certificate.
The other is that in case the above attempt proves to be futile, wait till your termination and agitate it legally under the ID Act,1947 if you are a workman or if otherwise, institute a Civil Suit to declare the orders of termination null and void and get a declaration to that effect. Of course the second option would be a long-drawn legal battle provided you have the time and wherewithal.
My suggestion, therefore, would be to sort out the issue amicably so as to retain your employability intact.