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Telecom is planning to upgrade its mobile data network in Wanaka this year.
Residents and holiday-makers trying to use their mobile devices complained of congestion during New Year celebrations, and the problem has arisen again during this week's Challenge Wanaka triathalon.
A Telecom spokeswoman said the company was aware of the increased demand this week, which was similar to the New Year period.
''Regrettably, there is nothing we can do to ease congestion at present but Wanaka is due to get a capacity upgrade this year in light of its increased mobile traffic.''
The spokeswoman said Telecom had not finalised its ''build date'' yet but hoped to have something in place before the ski season.
''The heightened demand is being driven by the rapid pick-up in smartphones among the public.
''We're noticing this not only in Wanaka but nationally as more people utilise smartphone technology, download apps, send emails and access online tools.
A Vodafone spokeswoman said its network was also ''incredibly busy'' and the company would be shifting some of the traffic to its Treble Cone site to reduce congestion.
The main issue was with the 3G data network handling internet traffic.
The spokeswoman said Vodafone was always happy to put temporary cellsites in place but it needed to be advised of an event in advance.
One temporary site was in use at present in Invercargill for a motorcycle event.
A Wanaka Vodafone customer spoken to by the Otago Daily Times sought, and received, a partial refund because of the congestion at New Year.