Spark's fighting back against fraudsters targeting its customers.

People have been receiving phone calls from scammers, using a security threat to gain personal information and steal people's money.

Spark's Chris Quin told Newstalk ZB's Larry Williams the company is doing its best to stamp out the scam.

"We've managed to find some of the phone numbers overseas they are calling from and get them shut down."

But he says there could be many more, and people need to contact Spark's new scam hotline.

"Just calling our normal 123 number and taking option nine on the IVR customers can get straight to a help desk that is focused on helping customers with us and recording the report."

The scammers have been mirroring how Spark operates, to trick customers.

But Mr Quin says people should never hand over personal details, especially bank account details.

"Like all of the industry we're very clear with customers we will never call you and ask you for those sort of details."