Non refund of security deposit


Google Fiber Calling :)
I am following up nextra for refund of my security deposit since August, 2019 which was given to them back in 2013. More than 4 months has already passed and they are doing nothing. It is surprising that their nodal officer and appellate authority even stopped replying to e-mails. Anyone on this forum got refund of security deposit from Nextra? I never expected Nextra to be so bad.