In August, the competition watchdog asked retailers to fix "frankly terrible" advertising with an aim to stop public confusion due to the practice of marketing maximum internet speeds achievable in off-peak hours.

These optional guidelines have already seen some retailers pick up their act, Australian Communication Consumer Action Network senior policy adviser Rachel Thomas said.

"But we are still waiting for a number of providers to make progress," Ms Thomas said.

"Having a choice of speed is a new thing. You need to know how many devices, how fast you want, the average speed, the peak speed ... this can translate into the speed you end up getting in many different ways," she said.

"It's important consumers are aware there is one speed during peak hours and a maximum speed."

Telstra was one of the most advanced in updating their marketing, she said, by including the type of peak hour speed and maximums that can be achieved.

Action was recently taken under Australian Consumer Law against Telstra, with 42,000 customers being compensated earlier this month for slow NBN speeds.

These refunds were to a group of customers who were sold services where their NBN line was not capable of delivering the chosen speed tier.

A Telstra spokesperson confirmed they changed the names and descriptions of their NBN plans in October to align with the new guidelines - including minimum speeds customers can expect at peak network times.

"The actual speed tiers remain the same, however we have changed the way we describe them," the spokesperson said.

Since the ACCC undertaking, they've identified 4 per cent of customers connected to the NBN whose connections are not available of delivering the top speeds - these customers have begun to be contacted and will continue to be contacted over the remainder of November.

Retailers were encouraged to "immediately" implement some measures in August, by the Australian Competition and Consumer Commission, but a spokesperson acknowledged it would be reasonable to allow three months for more significant changes.

They would "monitor market developments in the coming weeks" to determine compliance, though had already seen some telco companies move towards compliance and were aware of providers who were still intending to follow suit.

Industry peak body Communications Alliance chief executive John Stanton described the guidance as "voluntary and very complex" and said it could be too early to say whether it has had a positive impact.

"Service providers have been assessing the practicality and challenges of complying with the ACCC guidance," he said.

"Challenges including re-working all existing media, creating new network testing processes and deciding whether to start renaming broadband plans with the names suggested by the ACCC," he said.

He also raised doubts as to whether some descriptions - such as 'Standard Plus Evening Speed' - were particularly marketable.

An Optus spokesperson confirmed they'd commenced updating their NBN advertising in line with the ACCC's guidance.

"Optus NBN advertising utilises industry standard speed labels which provide customers with information including maximum off peak speeds and typical evening peak speeds they can expect," the spokesperson said.

ACCC chairman Rod Sims said they had seen significant changes in the market as telcos moved towards compliance - with some providing evening period speed information in their advertising.

"We are aware of other [providers] that are intending to follow suit," Mr Sims said.