I am using AIRTEL sim card from 7 years. They provide great network across India & have awesome helpline support 24 X 7.
Providing good daily plans, tariff plans, data plans, etc. The Internet speed is awesome as they providing 2G, 3G & the first operator in India to launching 4G . I have never faced any problems about anything related to unnecessary balance deduction which the others operators mostly do.
The best thing about airtel is that you can use your internet data packs even if your balance is **ZERO** & balance never becomes negative.