here is the whole story how I came to know about the price hike.
I recharged my account in july with rupees 4300 and my due date was adjusted accordingly. Being an international customer I mail airtel cc to activate 6 months advance rental magnum hd pack to get extra 15 days. They replied that your balance is not enough, 6 months advance rental magnum hd costs 4450. Then I mailed them back to say that the same pack costs 590/month thus 6 months will cost 3540. They replied again that magnum hd pack's revised price is 740 per month thus 6 months cost will be 4450. No pay per view channels are available in this pack like hbo etc.