BSNL is an government telecom company.The one and only reason to use BSNL is that it is roaming free and the call cost are verry low .
That’s it I personally use it for this purpose only otherwise I don’t have use Bsnl.
It has bad call quality and Sometimes it connects the call to unknown person which is very annoying .They have great network coverage but their speed is not good.Internet speed is verry-verry bad .Customer service always be a big problem of BSNL mobile network.If you call in service center minimum waiting .20-30 minutes.3G works like 2G and is very very slow.This is the most reliable network in the india.