Airtel — Sim stopped working suddenly overseas

On 16September 2021 afternoon, My airtel India sim stopped working suddenly. Its been 9 months since I started living in Tokyo, Japan and the network was working just fine. I had done all the essential recharges and kept it active. But on 16th, all of a sudden, the SIM stopped working without any intimation.
I used the airtel app to solve the problem initially but it suggested me to contact the customer support. Unable to call back Indian customer support(Sim not functioning) I tried Airtel's website to raise a complaint. But the website was equally not helpful and suggested me the same.
I then had to get in touch with aitel via their Twitter handle on 17thSeptember 2021, and after repeated tagged tweets, requests and Direct messages, they finally responded on 18th asking for the number.
I gave the necessary details and told them that I live in Tokyo, Japan, and also that all my bank and other essential accounts are attached to this number, so now without the number being active, I'm unable to receive OTPs and hence unable to access my accounts and do other essential works back home like paying electricity bills, Rent, send money to family etc. I requested them to help me quickly.
They came back with a suggestion to manually connect to networks that are provided in USA. Unable to understand their suggestion I reminded them that I live in Japan not USA. They later asked me to latch on to one of the two network providers in Japan. I tried both and the the Sim did not latch on to any of them. The sim also failed to setup a APN manually or take it automatically from any network provider.
Based on suggestion I checked my phone with other SIM's and my SIM on other Mobiles. My mobile was working fine with other sim's and my SIM although recognized as a SIM in other mobile(which it was not happening in my mobile), did not connect to any network and after few attempts to connect to the different networks, the SIM stopped offering me the list of network available even.
Now this happened on 18Sep2021 and since then, the Airtel support, Via Twitter messages were only repeating the same suggestions time and again, despite me telling them repeatedly that it was not working.
Its 27th September2021, 10+days from the day the problem occurred and yet Airtel have been very reluctant in helping me solve the issue or even give a sensible solution. They never come back with a solution proactively either and need repeated reminders to even respond; and when they do, they respond with the same message repeatedly to latch on to a network. I have been telling them that the mobile has stopped detecting any network even, but they does not seem to understand.
I'm not in a position to come back to India for a sim card leaving my work here. Nor can I wait for eternity to make my sim work. I need to access my bank accounts back in India and also many other essential services urgently but the network does not seem to be helpful at all.
I'm struck in a foreign land, cut off from India, especially my financials due to this issue. And scarily, because my SIM does not work, I'm unable to know if my bank account is being used by any miscreants. Even my investments are on hold because of this issue.
I have been a loyal customer of Airtel for more than a decade and the trust I placed in their network is wearing out. Now I'm scared of all the details I shared with them too. So I wish to hold Aitel responsible for any financial misuse if it happens, or any other issues with regards to delay in bill payments and/disconnection of services in India and wish to get my sim and also complete settlement of all related Issues.
I believe with perfectly working Mobile and untouched SIM, there is no other way that a sim could stop working suddenly, unless done deliberately.
And if this is how the network supports its expat customers, then how could we trust them and come abroad from our home? forget work, but even for a trip? They can disconnect us from any place anytime and we would be left stranded in a unknown country without a means to contact and inform anyone.
I want my Sim working back, if they can't do it, I expect a new Sim to be delivered to my Home here, or at the least provide me an Esim, which could be used on my mobile. I need this issues resolved as early as It can be, as it has halted many essential transactions. Especially due to the services o[censored]sing OTPs to access multiple accounts.

I'm attaching my entire conversation with the airtel support below. I can attach the tagged tweets or app responses if required. (FYI, The Airtel app does not even have an option for SIM not working scenarios).

Please contact me at: [protected]@gmail.com

Regards,
Sujal Bhandary