Australians are making fewer complaints about their phone and internet services but, when things go wrong, they're taking longer to be rectified, according to new data from the Telecommunications Industry Ombudsman.

The TIO's annual report shows it received 132,387 complaints from consumers and small businesses during last financial year, a 21.1 per cent decrease over the previous year.

However, in 2017-18, when complaints were marked unresolved and so escalated by the TIO, 77 per cent of them were closed within 60 days. In the past year that fell to only 47 per cent of cases, meaning half of the unresolved cases took more than two months to close following TIO action.

"The volume of complaints coming back to us unresolved shows an emerging picture of complexity in technical and small business issues," Ombudsman Judi Jones said in a statement, noting that special teams had been formed to handle those escalated complaints.