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Telecom says it will begin selling SIM cards for mobile customers using WorldMode phones overseas, but a fix for voicemail problems will not be available for 10 to 12 weeks.
Telecom's business solutions general manager Greg McAlister said problems receiving voicemail on overseas GSM networks meant the launch of the Telecom SIM cards for roaming-capable phones had been delayed until next week.
Only calls received while the phone was switched off would go through to voicemail when the user was on an overseas GSM network.
Unanswered calls or calls to an engaged phone would "ring out", said McAlister.
"Voicemail in GSM mode isn't up to what we'd want it to be, and we're further enhancing that," McAlister said.
"As soon as we're satisfied we've got the GSM voicemail working the way we'd like to see it, we'll let [customers] know. In the meantime we'll make it absolutely clear to them when they're turning the SIM on about the voicemail effects of GSM."
Telecom customers wanting to roam globally need to take a WorldMode phone, which works on Telecom's CDMA network as well as the more common GSM networks of its roaming partners.
Previously this has meant having two mobile numbers and voicemail boxes - a Telecom 027 number and a SIM card and mobile number provided by United Kingdom mobile company O2, Telecom's former roaming partner.
The company said it would have SIM cards for its WorldMode mobile phones available from next Tuesday, meaning its customers would need only one number when using a mobile phone overseas.
Shares in Telecom closed up 6c at $4.64 yesterday.
