Airtel - Airtel Number stopped working all of a sudden

My Airtel Number which I had gotten issued from Hyderabad, Telangana around ~ *+ years back had been showing 'No Service' since the last * months. For info, I permanently left Hyderabad an year ago and moved to Singapore(current location) last year December **** and had been using it (getting Alerts/OTPs etc) until * months back with no issues.
After following up with Airtel customer service over emails for weeks and doing all the possible steps as instructed by them all to no avail, I had been told that my sim became 'Faulty' a few days back and needed to be swapped.
They asked me to contact local store manager Varun Kapoor i.e. Kanpur (My Hometown). So my blood relative(Brother) went there with all the asked documents and got the blank sim issued on **th July ****.
I immediately sent the blank SIM number details to store manager with all the docs e.g. Aadhar,PAN,Passport,VISA etc on the same day and asked him to take it forward (To Hyderabad counterpart to link this blank sim to my number).
He has been extremely irresponsible and unprofessional during the whole process. He casually told that he forwarded my details after one week when I asked him for the update. Reason he didnt bother to give. He got some query on the same from Hyderabad team but he mentioned it to me after ** days. Reason, he casually said he 'forgot'. And even these updates I received when I mailed/whatsapped/called him many times.
Now he hasnt responded yet since * weeks after I sent him whatever he had asked for. Been texting/calling him since forever but he doesnt respond now. I really wish If I could escalate this matter against him to some authority so that he knows how to deal with customers.