Bharti Airtel - Did not refunding excess amount after MNP

I was previously having the postpaid mobile connection(**********) with Airtel company and now ported out from Airtel ( postpaid ) to Reliance Jio ( postpaid ) on ** Dec ****. I am having excess amount of Rs ****/- approx in my airtel account which was the advance payment that I had made. and When asked the Airtel company for the refund, but Company is not refunding the amount. I has already send the written complaint to the Airtel company via mail first they said they will credit the amount within ** to ** days and asked for the cancelled cheque. Later they have asked for the bank statement which was also provided by me. But now they are saying that they want the deduction statement from my bank. I have paid the amount through third party app thats why it is not available in his bank statement. Airtel also confirmed the receiving of payments in earlier bills, and final Airtel bill shows the excess amount. I have already complained to the appellate authority also with Airtel communications Reference No. ********.
My Last Airtel bill is attached for reference.

Kindly look into matter and help to get my money back from Airtel. Hoping for the earliest resolution.