Spark says some customers may have to wait up to two weeks for some faults to be fixed this winter.
Very wet weather recently has caused a sharp spike in broadband and landline faults experienced by Spark customers who rely on the Chorus-owned copper line network for their services.
The number of faults requiring a visit by a Chorus technician has almost reached the volume for the entire 2015/2016 summer only a few weeks into the winter season.
Spark is receiving more than 6000 fault-related calls per day, up a third from a few weeks ago.
Bridgette Dalzell, general manager of Spark Care, says broadband and landline services delivered via decades-old copper are highly vulnerable to wet weather.
"When copper lines get wet or damp, they either stop working or their performance deteriorates badly," she says.
She says Chorus has warned Spark and other service providers that customers might have to wait for up to two weeks to get faults fixed during the current winter.
This week Spark began hiring a further 130 customer care agents -- but it will take time to get them on board and fully trained.
"While we are committed to hiring more call centre staff today, our longer term focus has to be digitally based," she said.
As part of the digital initiatives, Spark is trialling a new system where it will proactively contact customers via text or email to advise them of any faults or maintenance taking place in their area, avoiding the need to call, Ms Dalzell says.