State-run BSNL Friday said that it has extended the scheme giving 80 per cent reduction in mobile rates to its existing customers. The company had earlier announced the scheme for new customers. In a statement, BSNL said, the call rates have been reduced for both per minute and per second billing plans and its tariffs are most competitive in the industry having largest network coverage. It added that two new special tariff vouchers have also been introduced.BSNL has taken various initiatives to improve its services and add more customers. The company has also gone mobile number portability positive with 1,57,564 people joining its network and 1,24,158 leaving its network between July to November period. At the end of September, BSNL mobile customer base stood at 79.6 million and the company figured among top five players in terms of new subscriber addition during the month.