Police have become involved in an investigation into how dozens of Telstra customers with numbers starting with 4963 were wrongly billed for calls to an internet gaming site.
Telstra's billing and security divisions have been investigating how several hundred calls to 1900 910 080 were made during a two week period last month.
The calls, billed at a rate of $13.97, were made to buy tokens to play the online game Runescape.
"Our investigation is continuing and we have now briefed police," Telstra's Hunter Region manager Chris Cusack said yesterday.
"We are also in the process of contacting all affected customers."
Telstra is also working with the company that provides online PIN numbers to play Runescape, Surfpin, and the site's manager, Cloudtel.
The telco has refused to release details of its investigation into the incident.
It is still not known if the fake calls, which have generally occurred late at night, originated within Australia.
A telecommunications engineer previously told The Newcastle Herald it was likely the calls were made using Caller ID spoofing technology.
The technology uses an internet-based server that can make telephone calls with false numbers.
Caller ID spoofing is the world's fastest-growing form of telecommunications fraud on landlines and mobile services.
An Australian Communications Consumer Action Network spokeswoman urged customers who suspected they had been wrongly billed for calls to contact their telco.
"It's unlikely that you are going to know it's fraud but you would hope your telco would know if there was some sort of fraudulent activity linked to your account," she said.