The Telecommunications Users Association says the cost of mobile calls to those on rival networks should continue to fall, due to greater scrutiny from the Commerce Commission and stronger competition.
The commission found the price gap between calls and texts on the same network, called on-net, and those to rival networks, called off-net, has narrowed, while the traffic of both has risen.
Off-net revenue for calls fell 2.6% to 37 cents per minute in the three months to October, while off-net texts fell 5.5%, to 3.4 cents per minute.
Association chief executive Paul Brislen says he expects the price gap to keep narrowing, particularly because Two Degrees is intent on lifting its market share.
He says the popularity of smartphones and demand for data on them could also change how voice and texts are provided and priced in the next year.
Voice calls and and text traffic rose 0.8% and 3.2% respectively.