Recovery amount for not serving complete notice period during leaving the company

I left my current company which had the policy to serve 2 months notice and if full 2 months notice is not served and the candidate wants to leave early he has to pay recovery amount for the shortfall of days. Example: An employee informs his manager of his/her intent to resign on July 1st ( verbally or via email). Ideally his last working date would be August 30th (with 2 months of notice). However the employee raises the separation request on Darwinbox only on July 21st. ( i.e. 20 days after his/her first conversation with manager) Hence the effective date of resignation will recorded as July 21st (as per the system). Based on manager's input even if the HR/Finance team considers the employee's Last Working Date is August 30th, as per records, there will be a shortfall of 20 days considered in the notice period duration. Hence the notice period shortfall amount i.e. 20 days of basic salary will be deducted from the employee's F&F settlement. this separation policy was introduced just 3 months before my resignation and the mail clearly mention only basic salary will be deducted from the employee's F&F settlement. Now the company is forcing to pay full amount not just basic salary as recovery amount saying it communicated wrong information. Can I take any legal action ?