MUMBAI, Feb 21 (Reuters) - Reliance Industries' RELI.NS Jio telecoms unit will start charging customers from April 1, but will offer sharply discounted prices for a year to those who sign up by the end of March, Chairman Mukesh Ambani said on Tuesday.

Customers who sign up by March 31 will be able to use unlimited data and voice services for a year at 303 rupees ($4.52) a month under a special offer, Ambani said. Enrollment to the plan would cost a one-time fee of 99 rupees.

Ambani also said Jio has added more than 100 million customers since launching its services last year. ($1 = 66.9650 Indian rupees)

(Reporting by Sankalp Phartiyal and Devidutta Tripathy; Editing by Rafael Nam) ((devidutta.tripathy@thomsonreuters.com; +91 84518 40430; Reuters Messaging: devidutta.tripathy.thomsonreuters.com@reuters.net))