The mobile phone network of Bharat Sanchar Nigam Limited (BSNL) was disrupted in several areas in Calcutta on Wednesday. Whoever tried to call a BSNL subscriber heard an automated message ? ?user is not reachable? or ?all lines in the routes are busy?.

Calcutta Telephones (customer services) general manager S.K. Bhaduri, however, denied there was any problem with the network. ?No such thing happened. We did not experience any problem today,? he asserted.

But BSNL sources admitted to the connectivity problem and said it arose out of an attempt to integrate two switching systems. The existing switching system does not have the capacity to support a major expansion, which is being planned. So, BSNL has introduced a second switching system, which is being integrated to the existing one.

?Network glitches crop up during integration of switching systems. BSNL can?t be blamed for this, as it can happen with any network. Nor can we rule out the possibility of such problems in future,? said a BSNL insider.

Holding out an assurance, he said the technical wing had swung into action and damage-control measures were being initiated on war footing.

Among the countless sufferers in the city on Wednesday was Manoj Singh, a resident of Tollygunge.

?My father is a cancer patient. I urgently needed to speak to the doctor who is treating him. I tried to call the doctor several times, but not once did the line get through,? recalled Singh.

People from all walks of life ? businessmen, government employees, policemen, doctors ? complained of similar inconveniences.

Speaking about BSNL?s expansion plans, an official said the CellOne connection would be given to another 600,000 customers in Calcutta and 700,000 across the state by March 2006. Investment in the project has been pegged at Rs 500 crore.

Presently, BSNL caters to more than 350,000 customers in Calcutta and around 650,000 in Bengal.

Orders have reached from Delhi to prepare the waiting list of prospective customers willing to have a CellOne connection. According to the market trend, 90 per cent of the new customers will opt for the pre-paid service, sources said.

?Unprecedented? growth in the past 13 months and a massive ?migration? of customers from private networks have forced BSNL to decide on building 300 base-transmitting stations in the Calcutta Telephones area, sources said.

Now, there are only 200 base stations in the CalTel zone, inadequate for the ?vast? subscriber-base.

?That?s the reason for frequent network congestions,? said an official.

Plans are afoot to have 900 base stations across the city and its suburbs by 2006.