Telstra customers made more complaints about their service provider than any other telco's users in the last three months, placing the company at the top of the TIO's complaint list for the first time in years.
According to the Telecommunications Industry Ombudsman's latest complaint statistics - from January to March - Telstra customers made 14,830 reports to the TIO about issues with their service in the last three months, a ten percent increase on the previous quarter.
However, compared to the first three months of 2014, complaints about Telstra fell by one percent in the most recent quarter.
A Telstra spokesperson said the telco was pleased its complaint numbers remained steady year on year, and said it had recently increased its efforts to be easier to deal with and deliver more value.
"This includes helping our customers get back to the person who initially served them, whether that’s in person, on the phone or online," the spokesperson said.
"We have [also] continued to focus on excess mobile data charges, and this week offer certainty for all mobile customers with the introduction of Extra Data. This is in addition to the introduction of real time data alerts in 2014.
"We know there is still much more we can do and we will continue our focus on improving customer service."
The figures put Telstra at the top of the list of most complained about telcos - a position that has consistently been held by Vodafone for the past few years.
But a concerted three-year turnaround effort which wrapped up last year has seen complaints about Vodafone's service drop.
The TIO's most recent statistics reveal the lowest number of complaints recorded about the telco since 2010 - the height of the 'Vodafail' saga.
Optus complaints still rising
Optus continued its bad run with a 44 percent rise in new complaints over the first three months of the year compared to the previous quarter, and a 50 percent rise compared to the equivalent quarter last year.
Optus said the increase in complaints was driven by delays in fixed installations and repairs, adverse weather impacts and disputed mobile bills.
"To address these issues, we are increasing our in-field technicians and customer service staff, and ensuring we educate our front line and customers on their mobile usage," a spokesperson said.
The spokesperson said the telco had changed its organisational structure last month to deliver a better customer experience, by introducing end-to-end ownership of planning, execution and customer experience.
"Products and services are now together with brand marketing to unite everything from product development to go-to-market execution," the spokesperson said.
"The customer area has united sales, customer service and digital altogether under one team to ensure a single and seamless experience across all customer touch points."
Complaints relating to the national broadband network also grew in the first quarter of 2015, predominantly due to connection issues.
The TIO received 15 percent more complaints in January to March than it did last October to December, at a total of 1635.
It attributed the rise to the growing number of premises being connected to the NBN.
Complaints fall overall
The number of complaints about telecommunications services and providers overall, however, fell by eight percent compared to the same quarter of 2014.
The figures are also lower than any other equivalent quarter since 2007, the TIO said.
New complaints about mobile services fell 20 percent year on year, as did reported issues about excess data charges, which were down by 42 percent.
However, the TIO reported a massive increase in new complaints about disputed third-party charges.
It counted 701 new complaints about issues such as disputed mobile premium services and other content services charges - a 77 percent jump year on year, and 88 percent more than the previous quarter.
Customers had increasing problems with landlines, registering 9305 new complaints about faults with the TIO - the highest quarterly number in two years - and 1501 reports of fully unusable landlines, up 13 percent on the first quarter of 2014.
Similarly, customers reported more problems with internet services in the first three months of this year than at the start of 2014, registering 8740 new complaints - a yearly rise of 28 percent - about internet faults and connection issues.
The TIO pointed out that it generally saw an increase in fault issues for internet and landline services during the third quarter of any given financial year as a result of seasonal weather conditions.
"There is the usual seasonal trend, with increased complaints for internet and landline services resulting from summer weather events.," the TIO wrote.