New Zealand Telecom is investigating claims that a Wanganui woman received a text message saying "F*** you" from its call centre after she complained about delays in her cellphone service.

Wanganui mayor Michael Laws took up the issue when a caller identified only as Vanessa contacted his Radio Live talkback show seeking an apology from Telecom.

Telecom spokesperson Nick Brown said that because of the serious nature of the complaint and any repercussions, his company needed to be very thorough in its investigation.

Telecom had spoken to Mr Laws this afternoon and was also getting in touch with the woman.

"Our customer service teams all set themselves the highest standards and therefore behaviour such as that reported by Mayor Laws would equate to serious misconduct," spokesperson Nick Brown said in a statement.

"We look forward to talking to Mr Laws and the customer directly so we can get the details and facts needed to address this serious complaint properly and quickly."

Mr Laws said the woman received the offensive message on February 6 after she complained her own text messages to family members were taking hours to arrive.

"Vanessa did complain after receiving the offensive text and tracing it to the Telecom call centre. But that complaint has remained dormant," Mr Laws said in a statement.

Mr Laws said he was increasingly concerned with the level of Telecom's customer service in the wake of further XT network outages affecting cellphones.

The XT network has suffered several outages since its launch last August.

A fault saw customers south of Taupo lose service for seven hours on Monday, with Telecom blaming an unusual pattern of text messaging traffic for the disruption.

Telecom is also offering $5 million in compensation to customers after the network went down twice in December and January.

"The level of communications and response to customer complaints has been abysmal," Mr Laws said.

*Source: The New Zealand Herald