Reliance Jio Infocomm will serve the country's largest and most sought-after accounts in telecom - the railways - from January 1, with officials saying it is likely to slash the national transporter's phone bills by around 35 percent at least.

Railways has been using Bharti Airtel for over six years as its telecom provider for 1.95 lakh mobile phone connections used by its employees in closed user group (CUG) across the country for which the railways paid around Rs 100 crore bill per year, they said.

Its validity will expire on December 31 this year.

A Railway Board order issued on November 20 said it "had assigned the responsibility to RailTel (railway PSU) for finalisation of fresh CUG scheme for Indian Railways as the validity of the existing scheme is expiring on December 31, 2018. Fresh CUG scheme had since been finalised by RailTel and Reliance Jio Infocomm Limited has been awarded the contract to implement the scheme."

"The fresh CUG will come into effect from January 1, 2019," said the order which detailed the tariff rates to be provided by the company.

Closed User group (CUG) is a supplementary service provided by the mobile operators to subscribers who can make and receive calls from any member associated within the group. This service is applicable for SMS also.

Under the scheme, Reliance Jio, the latest entrant in the telecom market, will provide 4G/3G connections and calls will be free of charge.

The company will provide four packages to railways - one for its senior most officials (two percent subscribers) - a 60 GB plan with a monthly rental of Rs 125, a 45 GB plan at a monthly rental of Rs 99 for its joint secretary level officers (26 per cent subscribers), a 30 GB plan at a rental of Rs 67 for Group C staff (72 per cent subscribers) and a Rs 49 rental plan for bulk SMS.

For regular subscribers, a 25 GB plan of Jio is available for Rs 199 and subscribers have to pay Rs 20 per GB thereafter to top up their plans.

Railway employees have to pay Rs 10 for 2 GB of extra data they use and more thereafter, according to the plan worked out by Jio.

While under the present scheme railways is charged for calls outside CUG, the plan from January 1 will not do so. Also, the 3G/4G data pack in effect from next year is much cheaper than the present packs available to railways.

"While Airtel is serving around 1.95 lakh railway subscribers, Jio will serve 3.78 lakh personnel of the railways, and because of the increase in the numbers, we are getting a better deal from the service provider. As a result of this, we are likely to reduce our phone bill by around 35 percent," a senior official said.