Spark isn't ruling out offering compensation to customers whose businesses were affected by a major cut in phone and internet services yesterday.
Tens of thousands of the company's customers nationwide lost all service because of a hardware fault and a failure of all backup systems.
Some said they'd called Spark's helpline for answers but waited on hold for hours.
Spark's chief executive for home, mobile and business, Jason Paris, said for most, yesterday's cut was an inconvenience, but for some, especially in business, the service was "a lifeline".
"If any Spark customers had an impact yesterday on their business, then give us a call."
Mr Paris said broadband was up and running again first and the mobile was progressively brought back into operation.
"But as a whole bunch of customers started to come back onto our network all at the same time it overloaded it and we needed to progressively bring them back throughout the day."
Mr Paris said the overloading problem stemmed from the fact that the back up system it not recognise there had been a hardware failure so did not redirect traffic to another system.
Because of that, technicians had to be called in to do a manual reset, which meant customers were off the network, and all came back on at the same time.
Mr Paris said services returned to normal late last night and customers should not have any problems today.
However the company has since said there were fibre voice call and broadband-related problems in the Auckland area this morning. A spokesperson said it was unclear whether the problems were related to yesterday's outage.