Bsnl has announced roam like home tariff plans from this independence day for all it’s prepaid users.
Which means benefits of all the STV or plan recharge are valid even while roaming India wide. 
All together no roaming STV required. Calls rate same as in home circle.
Bsnl is second operator to do so after Jio 4G. It was first to implement free incoming while roaming.
Catch is roaming tariff of 80p local/ 1.15p std would still be valid in Delhi & Mumbai where Bsnl sister concern Mtnl operates.
Irony of cheaper sms tariff (25p/38p vs Re.1/1.5) while outside of home circle still exists though sms STV are now valid in roaming also.