Complaints from mobile phone and internet users about excess data usage charges jumped more than 25 per cent last year, the consumer watchdog says.
The ACCC's annual telecommunications report, released on Friday, found 14,534 complaints about excess data usage were lodged with the industry ombudsman in 2013-14, up 27 per cent from the previous year.
"The top substantive complaint issue during the year was excess data charges," the ACCC said in the report.
It said complaints about the national broadband network also rose over the year, to 3982, reflecting the "expanded rollout of the network".
The watchdog said complaints about the NBN were about issues such as connection delays, faults and missed appointments.
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The ACCC said it would monitor both issues closely in 2015.
Most of the complaints to the ombudsman were about mobile phones (53 per cent), followed by landline telephones (25 per cent) and internet (22 per cent).
However, total complaints to the ombudsman fell 12 per cent, to 138,946 for the year, the report found.
It attributed the fall to fewer new complaints about mobile coverage, faults and customer service issues.
The report also found mobile handset downloads doubled between the June quarter 2013 and the same period in 2014, and that consumers downloaded "significantly more data during the year across all platforms".
The ACCC said prices paid by consumers for telecommunications services fell by 2.7 per cent in real terms in 2013-14.
The average real price paid for all types of internet services fell by 2.2 per cent, it said.
"Competition is driving substantive reductions in the price of telecommunications services, significant infrastructure investment to improve the quality and coverage of services, and technological innovation," ACCC chairman Rod Sims said.
