Flipkart — Refund amount of Rs 2980 not received

I made a flight booking on 11th March, 2020 via Flipkart travels using my Amex credit card. The flight was cancelled due to Covid-19 and i was informed that the amount is safe in credit shell. However, on 1st October, when i requested to use my credit shell, i was informed that airlines has cancelled the ticket and i will be getting a refund of Rs2980. I have been following up with Flipkart since then but still i have not received my refund. I made the transaction using my American Express credit card which i cancelled in July. So i requested the team to transfer the amount in my ICICI account. On 6th December i was informed that the refund has been initiated by them but it has been more than a month now and i have not received it. They are saying that they transferred it and provided a ARN number (Refund Reference Number: P60KG7A4226AJS00DQ) and to check with my bank. My ICICI bank confirmed that there is no such transaction and also that they cannot track using this ARN number. Flipkart is not providing the transaction id and also the mode of payment. I have written several mails and called them but they always share the same ARN number. Please look into this matter. I need my refund from Flipkart.