Airtel - Airtel charged me twice for a single transaction

Dear Sir,
My complaint is on Airtel pre paid recharge for which they have charged me twice for a single transaction and are refusing to give me a refund for the duplicate transaction.

I did a prepaid recharge for rs.*** (** days package) on March **th. However after the transaction completed, I was immediately charged rs.*** one more time for which I did not request. That means I was billed rs.***. When I spoke to Airtel representative on March **th Saturday, he said for the duplicate transaction, the money would be given back within * working days. However today when I again called up Airtel helpline and they said they will not give a refund and said do what ever you want and disconnected the call. Same with other representatives. Note: I have all the voice calls recorded on my phone. Please help me to get back rs.*** as I'm just a middle class man and that money means a lot to me. And Airtel being such a big company cannot cheat like this.

Kind Regards,
Arjun