How the iPhone's 'visual voicemail' can save money when you're travelling overseas

This week Telstra became the second Australian mobile carrier to offer Apple's 'Visual Voicemail' for iPhone, following Vodafone's introduction of the service almost two years ago.

Telstra is copping plenty of flack for its decision to charge $5 per month for Visual Voicemail (which it calls MessageBank Plus), especially since the feature is free on Vodafone. But if you're an international traveller, visual voicemail can actually save you money – even if you have to pay Testra $5 per month for the privilege.

Using your iPhone to check voicemail the usual way when overseas – dialling into your voicemail to listen to messages – can be a very expensive exercise because you're charged global roaming rates for calling your voicemail box back in Australia.

For example, checking your voicemail from China will cost $2.90/minute (plus a 40c flagfall) on Vodafone and $4.47/minute on Telstra.

The iPhone's Visual Voicemail system works differently. Instead of you calling home to listen to your voicemail, each voicemail message left for you is sent to your iPhone as a small, highly compressed data file - typically around 85KB for a 30 second message.

Australian Business Traveller confirmed this by activating Visual Voicemail on a Telstra iPhone 4, leaving a minute-long message and checking the iPhone's data usage before and after listening to the message: the result was a 170KB difference.

So instead of racking up roaming charges for calling back to Australia to listen to regular voicemail, on the iPhone you'll only be charged for the relatively small data transfer (also at global roaming rates).

Telstra charges 1.5c/KB for casual data roaming, so playing back a 30 second Visual Voicemail message on your iPhone would cost only $1.27. Vodafone's rack rates are 1c/KB, so the toll for a half-minute message would be 85c.

In both cases, using Visual Voicemail while you're overseas is much cheaper than the regular method.

Even allowing for Telstra's $5/month surcharge, you'd break even after playing back just six 30-second Visual Voicemail messages (for which the data roaming cost would be $7.62, while the voice roaming cost for a two-and-a-half minute call would be $13.41.)

Some countries have more reasonable rates than China for calling to retrieve voicemail, of course. Telstra's roaming rates for the UK are $2.95 per minute; in the US, $3.35 per minute; Hong Kong $2.95 per minute; and Singapore $1.55 per minute.

But in all cases of these common destination countries for Australian business travellers, receiving a visual voicemail on the iPhone is cheaper than making the phone call to listen to it.

All that being said, a word of warning: there are lots of ways the iPhone can chew up data quickly: checking your email, Twitter/Facebook updates, looking up the weather and so forth. By enabling roaming data while travelling, you run the risk of downloading plenty of other data apart from your voicemail messages.

To make best use of visual voicemail from a cost-savings perspective, you should only enable roaming data while also connected to a Wi-Fi hotspot such as a hotel lobby or cafe. The iPhone will use the hotspot for all data except the visual voicemail download, which keep roaming data usage to a minimum. (Visual voicemail cannot be accessed via Wi-Fi, only Telstra's global roaming internet connection.)

And of course -- don't forget to turn roaming data off after you've listened to your voicemail message!

danwarne