Previous employer asking for notice pay

Before responding your query it is advised to replace mode of addressing the experts obliging you in your query from "hi guys" to some respectable quote.

Dont pay notice pay instead ask them your full and final settlement or else threaten them that you will go to labour officer to file complaint regarding your dues

An employee is required to serve notice period or pay in lieu thereof in terms of his appointment. 

If you are willing to serve the entire notice period (hope it is mentined in your letter of appointment) and if the company has waive off part of notice period (hope you have written communication of the same), then you have a good case. In this event, you are not required to pay the notice pay since the same was waived off at the instance of the employer. 

It is advisable that first you take the full and final settlment (tactfully) and thereafter demand the illegally deducted salary against the employer using due process of law. 

If the company has waived the serving of full notice period by a written communication then the company cannot recover the amount towards the balance notice period.

You issue a legal notice demanding the return of the amount they recovered in this aspect.

Aftre that you can resort to legal action by filing a money recovery suit

fully agreed with Dr Vasistha