The Chief General Manager of BSNL (Gujarat circle) also has office on the seventh floor of the same building.
According to fire officials, the entire call center and the exchange room were engulfed in fire, which was doused within a couple of hours.
BSNL officials said that over 20,000 landline phone connections were affected due to the fire incident. Most of the connections turned dead, they said.
Technicians were trying to restore the electricity connection in the building they said, adding that the landline connections would be restored at the earliest.