Ihug customers are still experiencing major delays in connecting to the internet as well as having trouble reaching the company's call centre.
The internet problems have been going on for three weeks.
Ihug chief executive Mark Rushworth would not be drawn on how many customers had been affected,
but said it was in the thousands.
Ihug said on Wednesday that broadband customers would be unable to connect to the internet while its call centre had an overload of incoming calls. North Shore businesswoman Karyn Batchelor said it took her an hour to send emails on Thursday and she had been unable to reach the ihug call centre.
"Their office numbers and 0800 numbers ring disconnected because they are so overloaded," she said.
Her emails to business clients had been unanswered for two months.
"I don't want to switch providers but it's getting to the point where it is affecting the quality of service I can offer."
Claire Hurst, the manager of a motel in Northland, said her internet had been disconnected for several hours. She had tried calling the help desk but had been left waiting for 20 minutes, then 45 minutes before she spoke to ihug staff.
"We run a small lodge that depends totally on a functioning internet service as most of our bookings come via it. At least three bookings via email didn't reach us as people have followed up by phone after not hearing from us."
Mr Rushworth said the company's wholesale provider, Telecom, was causing the problem .
He had been trying to keep customers up to date about the issues, was working hard to resolve the problem and had installed new software to increase its queue capacity.
Telecom spokeswoman Melanie Marshall said Telecom had investigated and found no fault.
