Telecom regulator Trai has asked telecom companies to de-activate the international calling facility in pre-paid numbers and restore it only after a subscriber gives his explicit consent to avail this facility.

"Inform all pre-paid subscribers having ISD facility, through SMS, within 10 days of the date of issue of this direction, that ISD facility of the subscribers shall be discontinued after sixty days," Telecom Regulatory Authority of India (Trai) said in a directive to telcos.

"If such subscribers want to continue with ISD facility, they should give their explicit consent for availing such facility within 60 days of the receipt of the SMS," it added.

Trai has issued this directive following complaints from consumers about missed calls from international telephone numbers which are often premium numbers charging high tariff, prompting the consumers to make call to such numbers.

Trai said it has also been receiving complaints from consumers about receiving calls and SMSes from international numbers informing them about winning of prizes or lottery and prompting consumers to call a particular number to claim the prize or lottery money.

"These numbers are international numbers, which are often premium numbers charging higher tariffs. By responding to such calls/SMS the consumers have to pay unintended charges," Trai said.

The regulator has asked telecom operators to inform subscribers through SMS, within 10 days of the direction that pre-paid cellular mobile telephone service consumers need not respond to all missed calls from unknown international numbers or calls about winning prizes or lottery.

Trai has asked telecom service providers to send such SMS to consumers every six months and provide easy and transparent opt-in and opt-out facility to the consumers of the cellular mobile telephone service for activation or deactivation of ISD facility.