Over time without extra pay

It becomes illegal only when the employee does not accept it.  As long as Employees and Employer agree between them as to how to conduct their policies within the realm of existing provisions, there is no case.

At the point of joining they got us signed on lot of documents, I can still remember that there was one line where it was written that company can change its policy at anytime. And after the meeting in which company told that they will change the salary structure they got us signed on attendance sheet not on some bond paper. Is it still illegal ? 

Apparently not only you (the employees) but the employer is also ill informed.

The remedy might be possible.

OT is governed by the enactments applicable to the establishment/employer/employee.

Do you have any evidence of haveing worked for 14hrs/day e.g. deamdned by bosses,work reports,emails etc? Better you download it.

The employer would claim that employees worked on their own and to complete the pending work etc......?

Was any PF deducted and do you have salary slips?

Are you a meber of employee's unions,trade unions?

What is this establishment: Commercial,Industrial?

What is its line of business:IT,IteS,banking etc?

How many persons are employed in it?

The Redg Office,Corporate Office of the company is located in which state?

Does it have an office in Delhi e.g. Branch Office?

What was your designation and nature of duties?

Do you have leave policy, HR policy,Service Rules and Regulations,Conduct and Discipline Rules that are mentioned in the appointment letter?

Does company have its CO (certified standing Orders) and is your designation covered by CO? Or do Model Standing Orders apply to it?

Did the company obtain your signature on restrucuring of salary?

Do you have copy of restructured salary?

Has the company provided salary slip after restructured salary?