The sectoral regulator has also come out with conditional free national roaming plans, a move that will bring down cellphone roaming charges.
The changes will come into effect from next month.
"TRAI has reduced ceilings for national roaming calls and SMS and instituted a new regime for providing flexibility to telecom service providers to customise tariffs for national roamers through STVs (Special Tariff Vouchers) and Combo Vouchers," the regulator said in a statement.
It has also mandated two types of free national roaming plans to be provided by all telecom service providers. These changes will come into effect from July 1, 2013, it added.
"With increased subscribers and usage, the costs associated with national roaming have declined, but not vanished. There are still real costs incurred in providing the national roaming facility.
"Mandating a fully free roaming regime is simply not practicable at this juncture. Compelling a transition to a fully free national roaming regime would result in telecom service providers not being able to recover their costs from roamers," the regulator said.
In turn, telecom service providers would pass these costs on to all consumers (predominantly non-roamers) through higher tariffs, it added.
The ceiling tariffs prescribed by TRAI in 2007 were Rs. 1.40 per minute for outgoing local calls and Rs. 2.40 per minute for outgoing STD calls while on national roaming. These ceilings have been reduced to Re. 1 per minute and Re. 1.50 per minute, respectively, it said.
Similarly, the ceiling tariffs for incoming calls while on national roaming have been reduced from Rs. 1.75 per minute to 75 paise per minute, it added.
Tariffs for outgoing SMS while on national roaming, which were earlier under forbearance, have now been capped: outgoing SMS (local) at Re. 1 per SMS and outgoing SMS (STD) at Rs. 1.50 per SMS. Incoming SMS will remain free of charge, Trai said.
"TRAI feels that the best way forward is to establish a tariff regime in which roamers self-select themselves out and so minimise the impact on the rest of the subscriber community," it said.
In working towards free roaming, TRAI has also borne in mind the need to keep costs to roamers at a minimum, it added.
TRAI has decided that STVs and Combo Vouchers which were hitherto allowed only for home tariffs can be permitted for roaming tariffs. This will give the service providers the greatest possible flexibility in customising tariffs for their roaming subscribers.
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