"Across the board, all of the large companies have problems with customer enquiries and customer complaints." He named Telstra, Optus, AAPT, Primus, Vodafone and Hutchison.

However, Telstra was the target of about 36 percent of the 100,800 complaints - a relatively small amount for its market share. "Telstra, actually, relatively speaking ... is quite a good performer," he said.

He said billing complaints stemmed from companies not properly itemizing their charges.

Pinnock said complaints were consistently much higher in the telecommunications industry than in banking, insurance and finance.

Australian Mobile Telecommunications Association chief executive Graham Chalker said the number of mobile phone subscribers in Australia was nearing 19 million and the report should be looked at in context.

"The TIO"s Annual Report says there were 40,254 complaints about mobile phones in 2004-05. This is 0.2 per cent of total subscribers," he said.