Airtel — Airtel looting customers

I usually recharge my airtel number with pack of 449 to get truly unlimited calling and 2GB daily data for 56 days.
Yesterday, when I tried calling my banks customer care number for personal reason, I got voice message saying insufficient balance. I came across this scenario for the first time, so thought of checking with airtel customer care. But, there also I'm not able to reach them out just because they say there is not enough balance. I am able to do normal mobile calling currently. Now, below are my queries/complaints,
1. How come I'm falling short of any calling balance when I have already recharged my number 15 days ago with pack of 449(truly unlimited calling) as mentioned above?
2. What kind of talktime balance airtel needs me to recharge with to reach out their customer care?
3. I never faced such issue in past. So, how come all my balance finished suddenly?
4. When I tried to see balance deduction summary/history using *121*51#... I could see Rs. 60 deducted from my balance for using internet data. How is this valid when I have 2GB daily data of my recharge remaining ?

Looks like Airtel is looting customers now. Please help. Thanks.