Airtel — Failed recharge transaction but amount not refunded

Hello!
I made a transaction on Airtel's website for the recharge worth Rs. 449 dated 3rd March '21 for which the amount got debited but I was told my recharge failed. So, I contacted Airtel support regarding that and they assured me to proceed with a new recharge transaction and that the old disputed transaction's amount will be refunded back within 15 days.

I waited for the time being and still hadn't received any amount. So I contacted Airtel back and now they told me they haven't received any amount from my end and should contact my concerned bank.

I later contacted HDFC Bank regarding this disputed transaction and was assured they'll look into it and will get the amount back by 15th July '21.
The date has passed and I still haven't got my amount back.

Contacting the support is causing me a lot of strain and mental agony and I'm tired of going through this now.
It's been two months and still I haven't got any resolution for the transaction amount either from Airtel or from the bank.

I would really appreciate it if my amount gets refunded at the earliest or else I'll have to go with legal proceedings.

I have attached all the communication I've received from the bank and Airtel as well.
Also I am attaching my Bank statement for proof of transaction.