I tweeted to Airtel and said, I've 3 GB of add-on data but I'm unable to use it. I got a phone call from Airtel explained everything to them and it seems they understood.
This is the resolution they provided.
I'm not facing any network issues. I'm able to use daily data balance (1.4 GB/day). I've an add-on data 3072 MB. I'm unable to use that because internet stops working after consuming daily data. I really didn't understand how network refresh will fix it
I dropped an E-mail on Dec 9, 2018. Today, I got response from them other than "We're looking into the matter". So, it's due to a technical error and it'll be fixed soon (hopefully)