Phone bosses have pledged to send their customers annual spending summaries - plus a prompt to change plans if there's a cheaper deal that meets their needs.

They also say they will release a comparison tool to make it easier to compare plans between providers.

The changes are on the way after a shove from a regulator.

In September last year, the Commerce Commission released an analysis of 80,000 mobile phone bills that found:

• A quarter of post-paid (contract) consumers could save an estimated average of $11.60 a month by moving to a cheaper plan that would still cover their usage.
• 7 per cent of all residential consumers spent a relatively high amount on mobile services, given their usage, and that these consumers could potentially save an average of $48.65 a month.

New Zealand Telecommunications Forum Chief Executive Geoff Thorn told Heather du Plessis-Allan it'll be beneficial for customers.

"The one thing we can d is provide them with better information so they can actually make a choice, so when they do decide the products they want, they make sure they are getting exactly what they need."

Consumer NZ today welcomed the Commission's announcement.

"Without good information on usage and spend, it's much harder for consumers to work out whether they're getting value for money," Consumer NZ chief executive Jon Duffy said.

"Giving customers decent information on their usage is essential to ensuring the mobile market works well. We're pleased the industry has acknowledged this and has agreed to make changes."

The major telcos disputed the study's methodology, saying the ComCom's sample ignored people switching phone companies, who often change to a cheaper deal at the same time.

Regardless, in a pragmatic move to head-off regulation, the phone companies proposed voluntary changes during talks with the market watchdog.

In an open letter to Spark CEO Jolie Hodson, Vodafone NZ CEO Jason Paris and 2degrees CEO Mark Aue, released this morning, the Commerce Commission's Telecommunications Commissioner, Tristan Gilbertson, thanks the telco bosses for agreeing to introduce a series of reforms by the end of this year.

The highlights (which borrow from similar moves across the Tasman):

• to provide at least 12 months' usage and spend information to their customers
• provide an annual usage and spending summary to their customers including a prompt to consider whether they are on the right plan
• promote the development of comparison tools including a prospective consumer data right (CDR) to make it easier for customers to compare plans and providers.

"This is the first initiative in the Commission's new drive to improve retail service quality in telecommunications," Gilbertson said.

Technology Users Association of NZ (Tuanz) head Craig Young applauded the new measures and said, "We urge the operators to see this agreement as a minimum level to which they should provide information to their customers.

"Operators should see this as an area in which they can differentiate by offering clear information about the service received."