Bharat Sanchar Nigam Ltd's customers owe more than Rs 2,300 crore (Rs 23 billion) to the public sector telecommunications giant.
Mahanagar Telephone Nigam Ltd has more than Rs 240 crore (Rs 2.40 billion) as arrears from its customers in Delhi and Mumbai.
Leading the pack of defaulters are BSNL subscribers in Uttar Pradesh, who owe more than Rs 400 crore (Rs 4 billion) to the state-owned company.
Customers in Andhra Pradesh have to pay nearly Rs 270 crore (Rs 2.70 billion), while those in Maharashtra have accumulated arrears of around Rs 220 crore (Rs 2.20 billion).
BSNL has to receive more than Rs 180 crore (Rs 1.80 billion) and Rs 170 crore (Rs 1.70 billion) from customers in Kolkata and Gujarat, respectively.
MTNL subscribers in Delhi owe the company Rs155 crore (Rs 1.55 billion), while in Mumbai the public sector unit (PSU) has yet to realise Rs 90 crore (Rs 900 million) from its fixed-line users.
While both the PSUs have taken a number of steps to curb the incidence of default payments, most of the amount may have to be written off because in most cases the defaulters are difficult to trace.
"While we disconnect the defaulters, this does not get us the money because the dues remain unpaid," said a BSNL official.
He added that after disconnecting a telephone, legal action was also taken for recovering the dues but it took time.
BSNL has also set targets for officials at the circle level for the liquidation of outstandings, and their performance is monitored each month.
Special outstanding pursuit cells have also been set up at the circle level apart from a high-powered liquidation board.