Air India — No refund for more that 14 months

I bought 2 tickets Delhi-Leh-Delhi more than 2 years ago. I have tried more than 14 months to get refund and I'm still waiting. I sent at least 15 emails to air India and every time they told me that they will send me a refund in 2-3 weeks. They even lied that they already gave me refund, but i went to the bank, get official bank statement and sent it to Air India. After that they admitted that they didn't send me any refund. Every time I get the same mail from Air India - we will send you refund in 2-3 weeks. And it's now more than 14 months and I still haven't receive my money back.