Tata Docomo — porting from docomo to airtel - docomo billed rs. 5533 charges and still not providing any details

Address:

Pune, Maharashtra, 411036

Quick Summary of problem:

I was a Docomo Postpaid user and opted to Port from Docomo Postpaid to Airtel Prepaid. Because in Docomo there was no option to convert from Postpaid to Prepaid.
Airtel Prepaid worked for 3 days and then Airtel converted my connection to Postpaid and did not even intimate me.
Finally, with Airtel Postpaid Bill, I got Docomo outstanding Bill of Rs. 5533 which was not communicated to me anytime and Docomo / Airtel have no idea for which service this is billed but as per them I should clear my dues!!!

Details:

Jul 10: Got DOCOMO Bill, total outstanding amount upto Jul 10 was Rs. 103, I already paid Rs. 150 on Jul 9th, which somehow was not reflecting in Bill, so I did not pay again for this Bill of Rs. 103. I have Bills and all Payment confirmations.
Jul 13: Docomo SIM got deactivated because of Port request from Docomo to Airtel Prepaid
Jul 14: Airtel Prepaid plan started, paid Rs. 495 for 84 days validity. I have SMS for same.
Jul 15: Airtel Prepaid plan continued, I checked the details in Airtel App
Jul 16: Airtel Prepaid plan continued, I checked the details in Airtel App
Jul 17:
My SIM Internet got stopped; When I checked Airtel app (using WiFi), it was showing as Airtel Postpaid. When I called
Airtel customer care they told me that there was request for converting this number from prepaid to postpaid. Though, I tried to convince them (for 2-3 days in multiple calls and call backs) as I have not requested for Postpaid, they said they cannot find from where request has been received but It cannot be converted back to Prepaid at least for one month after a Billing cycle is completed. I need to pay Postpaid Bill for at least a month.
I had no option but to wait. My mobile internet (postpaid) was also not working in this period. And internet from Prepaid plan was also stopped as I was no more a Prepaid user.

Jul 18:
I was travelling (by car) from Pune to Mumbai by road and when I needed Mobile internet most for using Google Maps, my internet was not working. Around evening, my internet started for Postpaid plan

Somewhere in Jul, Docomo was aquired by Airtel. If I have known this earlier, I might not port from Docomo to Airtel.

Aug 13:
I received Bill from Airtel Postpaid for total amount Rs. 5828.91.
When checking, there was TATA Docomo previous balance of Rs. 5533 for which no details are provided
I visited Airtel Store in Kalyani Nagar for this extra Billing charge, they said they have no information as its from Docomo (but Docomo is now Airtel). And I should pay as this is from Docomo and it was not paid by me.
If I need details of Rs. 5533, then I should visit any Docomo store for details information.
I visited 2 Docomo stores in Pune but both stored / shops were closed. They told me (over phone) that Docomo is now acquired by Airtel and so they do not have any Docomo business now.
I tried to connect Docomo Customer Care but those number do not work anymore.
I tried to access Docomo web portals for support, but they are being redirected to Airtel web portal

I contacted Airtel customer care on phone multiple times, but they say that I should pay Rs. 5533 as its from Docomo and it was not paid by me. As per them, they have no detailed information about Rs. 5533 and also still they do not know why my connection was converted from Airtel Prepaid to Airtel Postpaid.
As per Airtel, my connection can be converted from Postpaid to Prepaid only after I pay this Total Bill.They cannot help in providing details of Rs. 5533.
I got one working customer care email ([protected]@tatadocomo.com) of Docomo. I shared the complete experience to them. At least they replied. But reply was that as number is ported now, we do not have any details available and I have to pay Rs. 5533 outstanding bill.
Below questions are not answered by anyone.
1. How Docomo does not have records once number is Ported? They can tell Airtel that please charge Rs. 5533 for this number but they do not have details about why to charge this huge amount from a user having Rs. 299 plan?
2. How can Docmo allow to port if Rs. 5533 is outstanding?
3. Why Docomo has not send any email / communication to me that while Porting that Rs. 5533 was outstanding?
4. If my Docomo Postpaid plan is for unlimited calls and unlimited internet (internet speed decreases after total cap, and bill amount does not increase), AND Billing amount upto Jul 10th in Rs. 103 THAN how for Jul 11th and Jul 12th, Billing becomes Rs. 5533?
5. If Airtel is taking Port request and asking me to clear Bill of Docomo, why Airtel is not updating me early that still Rs. 5533 is pending?
6. If Airtel has acquired Docomo, why it’s so difficult to get detailed break-up of Billing amount Rs. 5533?
7. In my Bill, Credit Limit for my number is Rs. 1300 than how can my Bill shoots to Rs. 5533, and still, I have not intimated?
8. If Airtel is converting a user from Airetl Prepaid to Airtel Postpaid, why not they call and confirm with user? Or at least intimate by SMS that, “ok, Welcome to Airtel Postpaid”? Why user has to find out “Oh! Somehow I’m a Postpaid user” Again!!

Aug 27: 
Multiple emails and communications done but still Docomo and Airtel have not provided why they charged me Rs. 5533. But they are asking me to pay otherwise they will Stop services for my mobile number. My last 14 months total Bill less than 3 days Bill of Rs. 5533

This is totally wrong and unfair. This amount of Rs. 5533 should be waived off.

I have all Bills and Payment receipts but I'm not attaching it here as that will be visible to all. I can share with respective team as and when needed.

Please help!!!

Number for which there is issue [protected]