Air India — Refund of cancelled ticket

Address:

23 kovan road 548193

I booked a ticker for travelling from Delhi to Singapore for 18th Dec. The flight was postponed to 19th Dec and i was informed by an email. as my travelling to Singapore on 18th Dec was must, i booked another ticker for 18th Dec. Ticket with Air India was cancelled by Air India on a phone call (on 04th or 05th Dec) and i was told that i will get my money back with in 2 weeks.
i have been following up with Air India for last 4.5 months but nothing is happening. email replies are standard reply that we wil get back to you.
even on phone call, there is no firm reply. They just say its in process. i have sent many emails and have made multiple phone calls. i have also filled up feed back form multiple times.
Kindly assist me in getting back my refund.