Vodafone has apologised to Bay of Plenty customers affected by a network failure on Saturday.

A fault was triggered during an upgrade to cables between Taupiri and Horotiu in the Waikato on Saturday morning, about 8.30am.

The fault affected 16 cell sites in the Bay of Plenty, with some having 2G and 3G capability disrupted intermittently.

Customers suffered "degraded performances" and some calls and text messages were not connected immediately.

The sites were all back up and running by 2.40pm on Saturday.

Vodafone said it was fully focused on ensuring the issue did not happen again.

The problem followed a series of outages plaguing competitor Telecom's XT network this year, and as Vodafone launched a promotion for XT customers to take their mobile number to "NZ's reliable mobile network".

Four outages since Christmas had disrupted services to XT customers below Taupo, sometimes for days at a time.

Telecom has said it will pay $10 million in compensation to customers following the faults, which had caused clients and the Government to question the new network's reliability.