I have been using Bsnl for quite a long time now and what I love the most about this is the data pack they offer. For only 78 rs you get 1 gb data pack for 5 days and there are many more offers like cheap local packs. In Assam Bsnl is quite popular and the network is also fine.
Although at times the network disappears without any reason, but I am going to stick with it. For me BSNL is the best.