I am using airtel from last 3 years.
Its a postpaid connection and a corporate card.
It is a nice network not like Reliance telecommunications(which is commonly known as Rcom) which deduct money for unknown reason any time.
I too got problems some times but they resolve it at given time.And what I love in airtel is there Transparency it is best thing in this.Also there outlet / airtel customer care centres are in good quantity.