BSNL has turned out to be a wonderful mobile network i’ve used as for as the coverage is concerned. Here are some examples. No disconnections from Network while travelling from Kanyakumari to Bangalore by road Via, Tirunelveli, Kovilpatty, Sattur, Virudhunagar, Madurai, Dindigul, Karur, Namakkal, Salem, Dharmapuri, Krishnagiri, Hosur and Bangalore. The network strength is almost full always. But, in Madurai and other big cities, coverage inside buildings is poor. You often become not reachable. When it comes to Network is concerned, You will not be able to make any calls without seeing the network busy message atleast thrice. And at times you will not be able to make calls at all. Incoming calls, will give you a beep and register as missed calls. Without getting 5 missed calls no incoming call connect successfully. Soming to SMS. You can send SMS to almost all networks and you cannot receive messages from Airtel Network. Most of all, any messages sent using the CellOne menu in the Sim card work. So, you cannot even check for cricket scores. So the suggestion if you are going to move to BSNL will be to Wait till BSNL upgrades it’s backbone to hold more calls simultaneously. As for as billing is concerned, I cannot comment as I have to receive my bill yet and it’s 5 days since it became one month of usage. Helpdesk probably would be a plain woodendesk. The service number in the mobile is mostly Not reachable and there are no tollfree helpdesk numbers