According to Kantar's most recent report, Telstra remains the top mobile provider in Australia, holding 39.7 percent of the total market as of September 30, though this signals an overall decrease from the 40.3 percent market share recorded in September 2014 thanks to a drop in post-paid customer numbers.

"Whilst Telstra continues to outperform the rest of the market in the prepaid sector, and enjoys significant share gain in the smaller no-contract market also, such share gains are not sufficient to outweigh the decline seen in the key post-paid market, where share has fallen by 1.2 percentage points," Kantar said.

"Telstra does, in fact, have the highest level of customer loyalty among its post-paid customer base, at 96 percent, but, among those who churned, 26 percent switched to Optus and a further 18 percent to Virgin, with 67 percent of all churners remaining on a post-paid tariff -- however, 20 percent replaced their post-paid tariff with a no-contract plan.

"Cheaper calls, followed by better customer service, are cited as the key reasons for changing networks. Other noteworthy beneficiaries of the Telstra churners are Amaysim, TPG, and iiNet."

Optus came in second overall, at 21.4 percent of total mobile market share, marking an increase of 0.5 percentage points year on year; Vodafone Australia was third, accounting for 15.1 percent of the market, down 1 percentage point from this time last year; Virgin was fourth, at 5.7 percent, a drop from last year's 6.8 percent; Amaysim came in fifth, at 3.8 percent market share, up 0.1 percentage points; TPG was sixth, with 2.4 percent, down slightly from last year's 2.8 percent; and Aldi Mobile was seventh, holding on to 2.2 percent of the market, up from the 1.7 percent recorded last year. Other mobile virtual network operators (MVNOs) accounted for 9.7 percent of the total market, a rise of 2 percent year on year.

Kantar reported a continued growth across the no-contract sector, with that segment now accounting for 11.9 percent of the total mobile industry, up 8.8 percent since September 2014.

Telstra's numbers in the no-contract segment jumped by 6.9 percentage points, to 31.9 percent, while Optus lost 1.1 percentage points to hold 17.7 percent of the market; Vodafone rose from 8.8 percent up to 9.9 percent; Virgin was down 1.4 percentage points, to 5.4 percent; Amaysim gained 1.4 percentage points, to account for 8.7 percent of the market; TPG lost 1 percentage point, down to 7.4 percent; and Aldi rose from 0.8 percent up to 1.3 percent of the market. Other MVNOs dropped by 6.1 percentage points, down to 17.7 percent of the no-contract market.

In the post-paid sector, Telstra fell by 1.2 percentage points, down to 41.4 percent of the market; Optus rose by 2.1 percentage points, to 22.7 percent; Vodafone rose by 0.5 percentage points, to 16 percent of the market; Virgin sank by 1.5 percentage points to 6.1 percent of the market; TPG dropped 0.9 percentage points to account for just 2 percent of the market; Amaysim stayed fairly level, losing 0.1 percentage points to retain 1.4 percent of market share; and Aldi rose by 0.9 percentage points, to 1.1 percent of the market. Other MVNOs accounted for 9 percent of the market, gaining 1.5 percentage points year on year.

In the prepaid market, Telstra was up by 2.3 percentage points to 39.9 percent market share; Optus was down to 20.9 percent; Vodafone was up to 15.1 percent; Virgin fell to 5.2 percent; Amaysim dropped to 5.8 percent; Aldi rose to 4.5 percent, and TPG dropped 0.6 percentage points, down to just 1.2 percent of the market. MVNOs rose by 0.2 percentage points, to account for 7.2 percent of prepaid market share.

Kantar in April similarly recorded a jump in the no-contract market, up 2.1 percent quarter on quarter to 9.5 percent of the total market.

"Australian consumers are becoming increasingly exposed to the benefits of SIM-only tariffs, which offer 4G connections, rollover data, no lock-ins, and a generous amount of data, to name a few, for a comparatively low cost," Kantar said in April.

Telstra last month also held on to the top spot in a mobile network benchmark survey published by testing company P3 Communications and technology publication CommsDay, with the highest call quality and fastest data speeds overall, followed by Optus and then Vodafone Australia.

The MVNO sector is continuing to grow, with Kogan Mobile last month relaunching on the Vodafone network.

Kogan Mobile's 3XL plan will provide 3GB of data and unlimited national calls, texts, and MMS for AU$29.95 over 30 days, AU$79.95 over 90 days, or AU$299.95 over 365 days, while the 5XL plan offers 5GB of data and unlimited national calls and texts for AU$36.95, AU$99.95, and AU$369.95 over the same periods of time.

Vodafone last month also announced that it had signed a AU$1 billion deal with TPG to shift its 320,000 mobile customers from current provider Optus to Vodafone, with customers being offered bonus data as an incentive to move networks.