Australia’s favourite online retailer larrikin is at it again, not just waging war with the prices of electrical goods, but now going after mobile pricing with what appears to be a better deal than any other telco. So what’s the catch?

Launched last night amidst speculation that the company was working with Telstra, Kogan’s mobile service went live, offering a variety of SIM cards – the regular “mini” SIM used by most phones, microSIMs, and even the iPhone 5’s nanoSIM – to match two plans spread out over different needs.

“Australian mobile phone plans have been among the most confusing in the world,” said David Shafer, Kogan’s Executive Director.

“In the rest of the world, customers pay for minutes used or days of service. In Australia, we’re given slogans like, $49 for $500 worth of calls. These are empty slogans that don’t mean anything and are specifically designed to baffle and bewilder the Australian public.”

Three options are available on Kogan for the regular needs of a smartphone – voice, text, and data – with each offering the same thing, just spread out over a different set of time.

Offering unlimited SMS and MMS across Australia, unlimited calls within the country, and 6GB of data per month, the Kogan plan costs either $29 for 30 days, $79 for 90 days, or $299 for the entire year.

People who don’t need the phone service and are content with just data only – useful for tablets – can grab a data-specific plan from Kogan for $10 per month with 2GB included.

There’s no international roaming if you planning on taking your phone on vacation, but outside of this, the plans sound like a good deal, and Kogan is using one of the most reliable telcos in Australia, with Telstra confirmed to be supplying mobile service for the Kogan service.

But therein lies the catch.

While Telstra currently operates a high-speed 4G network capable of reaching in excess of 30-40Mbps download and previously pushed out 3.5G speeds of over 10-20Mbps, Kogan’s use of the Telstra network only offers the barebones basic 3G speed, which even Kogan’s terms cap at around 7.2Mbps.

Even if you have a faster 3G phone – and most of the phones these days are – you won’t pull down speeds higher than this, with most peak speeds sitting around 550kbps to 3Mbps.

That’s not a big problem if you’re not doing a lot of downloading on your mobile device, but if you’re used to speeds past the 5Mbps mark, you won’t find it here.

Where this could work really well, however, is with seniors and kids, groups of people who don’t necessarily need to have the whole of the world wide web downloaded to them immediately, and, like, right now.

With a plan just a hair short of $300 for the year offering unlimited calls, texts, and 6GB data on a slower network, it could suit your grandma, grandpa, teen or pre-teen quite fine, and you won’t have to worry about being one of the numbers in another “bill shock” story put out by the news networks.