The misuse was detected by the BSNL last week, following which the Raj Bhavan officials filed a complaint with the Cyber Crime Police Station here.
An amount of Rs 38,233 was billed due to this unauthorised use and it was being recovered from the system vendor, a statement from Raj Bhavan said.
It added that Gateway Business Solutions, the vendor of Matrix EPABX Systems, was in the process of installing an additional exchange and integrate it with the existing EPABX during this period.
"We have started investigation. We are getting information from the concerned officials," said Inspector General of Police (CID) Charu Sinha.
