Airtel - Internet data theft

I am a doctor in New Delhi and i do online consultations as well. So I am using Airtels *** plan which provides me * GB data every day. I also use Airtel broadband at home. On the morning of **-**-****while I just arrive at my hospital I cannot connect to the internet. Switched the phone on and off multiple times to see if it's some network issue. The problem persists and I call up Airtel customer care and they inform me that Suddenly in the middle of the night at ~ * AM my internet data qouta of *GB per day gets used up, God knows where, while I am asleep. Next day in the morning I am left without internet connectivity, missing out on all my online appointments and online consultations. Would Airtel care to explain why did they steal my data leaving me without internet making me lose on my patients and in turn them suffering because of it?