Telecom shuts down its 025 mobile phone network at six o'clock tonight, after a three year winding-down operation.
From tonight, people with 025 phones will not be able to make or receive calls or text messages, including emergency calls using a 025 mobile.
Telecom says any unused credit will be transferred to customers who switch to a new 027 connection.
Some 200,000 customers have made the switch, but there are still 20,000 who have not.
Rebecca Earl, Telecom spokeswoman, says some people have still not worked out that their 025 phones will will be redundant after tonight.
The network began in 1987 when mobile phone services were introduced.
- NEWSTALK ZB