Group Term Insurance Given By Employer

I work in a central government institute (Indian Institute of Technology). The institute enrolled all the employees in a group term insurance plan of a private insurance company without the consent of the employees on 1st May 2020 for the entire duration of their employment and started deducting the premium from their salaries. When the employees objected to this, the institute said that they need to remain enrolled till 31st April 2021 and those who want to opt out of this insurance were give an 18 day window to fill a one-time opt out form in January 2021. I missed that window and the institute now tells me that premium will be deducted from my salary for the next 25 years and I can never opt out of this insurance. Legally speaking, does the institute have the authority to do this.