Vodafone Prepaid — STD Call Charge changed

The STD Call Charge for Vodafone Prepaid Service is Rs. 1.30 per minue. This was the charge i was paying till now. Suddenly, they have started charging Rs. 1.50 per minute. I have niether changed the plan nor anything else. Also, the vodafone- India website does not display the toll-free customer care call centre no.
There are regular auto-calls from them. The regular calls are disturbing and call-drop rate is very high. It is unarguably the worst service provider.