A third of complaints made by telco consumers to the sector's ombudsman remained unresolved at the end of the latest reporting period.
The figures, between July and September of 2024, found 30 per cent, or 3,389, of complaints returned unresolved after a referral to a telco in relation to issues including poor customer service, problems with bills or equipment, and service drop outs.
This followed the Telecommunications Industry Ombudsman (TIO) beginning a new follow-up process with consumers to get a better picture of resolutions at the end of the referral period.
Ombudsman Cynthia Gebert said the high number of unresolved complaints pointed to telcos failing to address complex or multifaceted problems for their customers.
"This is the first quarter we have reported on this data in this way, and it is concerning that such a large volume of problems referred to telcos remain in dispute," she said.
"Our focus will be on restoring trust and confidence between the telco and their customer, and getting problems fixed."
A total of 13,541 complaints about phone and internet services were lodged between July and September of 2024.
This figure constitutes a 4.6 per cent increase on complaints in the same period in 2023, or a total of 599 additional complaints.
More than half the complaints made by customers related to no or delayed action from a telco, followed by complaints about service and equipment fees and complaints about no phone or internet service.
Complaints raised in relation to failure to cancel a service, where a customer claims a telco has not terminated an agreement properly, jumped by seven per cent since the previous quarter.
Ombudsman Cynthia Gebert said customers continued to experience persistent challenges.
"Customers are contacting my office because of patchy service and dropouts, telcos dragging their heels when it comes to fixing something, and poor customer service experiences. It's very frustrating for customers", Ms Gebert said.
"We saw a drop in overall complaints last financial year, which is a positive sign for both customers and telcos. It's disappointing to see the numbers jump back up, reporting the same persistent problems"
Nine in 10 complaints were made by residential consumers and 10.8 per cent were from small businesses.
More than 60 per cent of the complaints made by small businesses were related to no action or delayed action.
The top five local government areas with the highest number of complaints were Brisbane (426), Gold Coast (279), Moreton Bay (251), Sunshine Coast (199) and Wyndham (198).
These five areas alone contributed 10 per cent of all the complaints received in this reporting period.
