Until April 30 CDMA customers who sign up to a 24 month plan on XT can choose from a range of zero dollar handsets, and prepaid customers will receive a free $79 credit with any XT device purchased.
Customers can check if they are on the CDMA network by calling *333.
Customers are urged to take their CDMA phone to a Telecom store so it can be recycled, with Auckland children's Starship Hospital the beneficiary.
The New Zealand Telecommunication Forum expects 800,000 phone numbers will been been moved by April. In the past five years 300,000 landlines and 500,000 mobile phone numbers have been transferred.
TCF said almost 13,000 mobile numbers are now being moved every month.
One of the winners of the number porting system has been 2degrees, which earlier this year reported 275,000 of its mobile customers had transferred from another company.
TCF CEO David Stone said switching companies was relatively seamless.