The company, according to the investigators, had two dedicated telephone lines -- software companies are allowed such dedicated telecom lines to countries abroad so as to be able to transmit data abroad -- which were misused for these call-back services. The company, in turn, ran its call-back operations from Bhikaji Cama Place and Shreshtha Vihar in the Trans-Yamuna area.

Both these offices, in Bhikaji Cama Place and Shreshtha Vihar, had around 125 MTNL telephone lines each, used for these call-back services. These lines, in turn, were patched to the parent company's dedicated line in the Noida software park, and used to route calls to the US. Around 20,000 phone calls had been routedthrough each of these phones since June, when the operations are believed to have begun. Based on the number of calls, the estimated revenue loss to the state-owned VSNL through which all international calls are routed is Rs 80 crore.

Under a call-back service, users from India wishing to make a call to, say, the US, call a local number which then connects them to the desired US number, and later bills them at a fraction of what one has to pay the VSNL. So, the caller will have called one of the two offices of this company, asked for a US number, which would then be routed through the dedicated line. The calling party would then pay a fraction of what it pays to VSNL for using this facility.

How lucrative this operation is can be judged from the fact that VSNL charges a mere Rs 15 lakh a year for a dedicated line for operators who have made close to Rs 100 crore for this.

According to estimates, VSNL's international operations have been falling by around 5 per cent per year due to diversion to suchcall-back service providers.