New Delhi, July 2: Telecom operators will roll out nationwide mobile number portability (MNP) tomorrow, which will allow customers to retain their mobile numbers while shifting between cities or operators.

At present, number portability is allowed only within a telecom circle. However, pan-India MNP will enable both prepaid and post-paid subscribers to continue using their numbers with any operator anywhere in the country.

For instance, a person moving from Delhi to Calcutta will be able to use the same number even when he opts for a new service provider.

To retain subscribers who are moving to new cities, Airtel today said it would process the porting request within 24 hours (except for customers moving to Jammu & Kashmir, Assam and the Northeast owing to security reasons).

According to Trai (Telecom Regulatory Authority of India) guidelines, the maximum time that an operator can take to process an MNP request is seven working days and a subscriber can withdraw the porting request within 24 hours of application.

Reliance Communications announced that it would offer "attractive and aggressive plans for both its prepaid and post-paid customers, as well as customers porting in from other networks, to ensure that this is a seamless and easy transition" without providing any details.

Airtel said it would also allow customers to transfer their balance in case of a prepaid number or carrying forward their unbilled/billed amount in case of a post-paid connection while porting their number to a new city. "To facilitate a seamless transition we will also allow our customers to enjoy free incoming on roaming, while their number portability request is being processed," said Ajai Puri, director (market operations) of Bharti Airtel.

Trai porting rules state that post-paid subscribers need to ensure that they have paid all dues. For prepaid customers, any balance amount will lapse at the time of porting.

"This is to ensure that no subscriber moves from one operator to another without paying his dues. However, in case of full MNP, if you are retaining the operator and only switching cities, any special schemes offered by operators to retain customers is their decision," officials said.

Full portability was initially expected to be implemented by May 3. However, the Cellular Operators Association of India had sought an extension to allow operators to make technical changes, necessary to implement the service. The ministry gave an extension of two months.

Operators feel they will gain subscribers because of a churn as there are no restrictions on moving to another telecom circle when changing operators.