Four major telcos have been slapped on the wrist for leaving customers without service while trying to move to the National Broadband Network.

The Australian Communications and Media Authority says Telstra, Optus, TPG and Dodo have breached service migration rules, with more than 1500 of their customers left hanging while migrating to the NBN.

ACMA rules state telcos must provide a replacement service after three days if a customer has failed to connect to the NBN.

The companies agreed in July to court-enforceable undertakings ensuring they introduce measures to better comply with service continuity rules.

All four will have to report to ACMA each quarter for 12 months.

ACMA chair Nerida O’Loughlin said connection failures could have a huge impact on livelihoods, with people relying on phone and internet for work and home.

“TPG, Optus, Dodo and Telstra have all let down these customers and effectively left them high and dry during the NBN migration,” she said.