Airtel — false bill after porting to different operator

Address:

560029

Hi Airtel,

This is really frustrating for me, the way you are taking revenge for porting from Airtel.
I ported my airtel postpaid number "8050xxxx56" to Jio around 17th March 2018. My last billing date was 12 March 2018 and the bill amount was Rs. 278. I had around 26GB of carry forward data + 10GB of current month's data in my account. The porting was successful but after some days I started getting calls from airtel regarding bill payment. They told me that I have Rs. 325 (Rs. 625 total - 300 security deposit) of bill amount still due and I need to pay that.
I had plan of Rs. 199 per month and around 36GB of carry forward data, then how come my bill can be of Rs. 625.

I tweeted to airtel regarding that, and got call from them telling that I should visit airtel office to clarify about it and since I had the carry forward data, they can only waive this.
Then I visited airtel office (Radha Krishna Tower, 7 & 8, Ground Floor, 154/11, Opposite IIM B Main Gate, Bann, Bannerghatta, Karnataka 560076), for this. They told that since the number is deactivated, they do not have access to the data and only Airtel Head office can help.

Then I visited airtel head office (55, Divyashree Towers, Bannerghatta Main Road, Bengaluru, Karnataka 560029), again I get the same reply from them, that they do not have access to my number's database and only nodal officer can help and gave me your email id.
Here is the audio recording of same: https://soundcloud.com/jay-krishna-jha/what-happens-when-you-port-from-airtel-postpaid-to-other-number-airtel-cheating

After wasting so much time here and there, I emailed nodal officer, but they also did not reply. Now I do not have any other places to go.
I will wait for a few days more and surely raise this issue in consumer forum with all my details.
My questions to airtel:

If there is a bill due for my number, why I have not received any bill for that amount either through email or SMS.
Since I already had carried-forward data of more than 36GB, and my plan was of Rs. 199 per month, how the due for 5 days become Rs. 625

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