BSNL is blocking incoming calls since long time I think, even before desperate operators like Airtel, VodaIdea started doing that.
BSNL has validity extension plans that are cheaper than others to keep the number active, last time I missed to recharge as they don't remind aggressively like other operators do and all incoming outgoing stopped. Even after recharging, they took 2 hours to activate outgoing and after complaining it took 2-3 days to activate rest of services like messages and incoming calls.