I am auser of BSNL from my class 8.that time I as living in a small area where only bsnl network was exist. ivisited many area and forest here all network badly affected but bsnl is one and only network exist there.
You will find gsm network while traveling in national highways and railways in odisha. like my area today also many area in odisha where you find BSNL is the only telecom service provider.
Bsnl tower are projected in deep forest location also.BSNL has also variety topup to reduce call charges.it is true that bsnl topup range is high but if you need coverage you have to compromise with this.