Reliance Jio is offering 1,000 minutes per month (28-day cycle) of free calling every month across all plans.
Ambani was ranked 13th in the annual Forbes' rich list for 2019.
Jio said that the telecom regulator TRAI is likely to initiate consultation process for revision in telecom tariffs.
The govt has taken a string of policy measures over the past couple of months to shore up the economy and revive credit.
Trai's move to reopen the deadline for ending charges for terminating calls on rival networks beyond January 2020.
Kumar Mangalam Birla, head of Vodafone Idea, had sent an SOS to the government earlier also for deferring statutory payments.
A total of 953 individuals, who crossed the threshold of Rs 1,000 crore across 41 industries feature in The IIFL Wealth Hurun India Rich List 2019.
London-based SP Hinduja and family, with assets worth Rs 1,86,500 crore, retained the second rank in the list.
The company in an emailed statement said: "There has been no transaction of purchase of shares".
The acquisition was pursuant to a scheme of arrangement not directly involving Reliance, the filing said without giving details.