Telstra is warning customers to be wary of telephone scammers following a fourfold increase in reports over the past year.
Scammers generally call customers at home and claim Telstra needs remote access to their computer to fix a fault.
They're generally seeking personal information, particularly banking details, Telstra said.
"The increasing number of these telephone scams is concerning," said Peter Jamieson, Telstra's head of customer advocacy.
"Customers should be alert to any attempts to trick them into disclosing their credit card or banking details over the telephone."
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One woman told AAP she had been targeted by scammers as recently as last week, when a man claiming to be from Telstra called and asked for remote access to a home computer.
The man's foreign accent and a suspicious echo on the line rang alarm bells, and the woman hung up before calling Telstra, which confirmed there was no issue.
Telstra advised customers to hang up and call Telstra's official number if in doubt about the veracity of a call.
Customers should never give remote access to a caller or disclose banking details over the phone, Telstra said.
The Australian Competition and Consumer Commission said scammers commonly prey on peoples' trust of government authorities and reputable businesses.
It warned Australians with disabilities to be wary of anybody calling out of the blue claiming to represent the government's National Disability Insurance Agency.
* People can report suspected scams to the ACCC by calling 1300 795 995.
