TPG Telecom won an auction to become the fourth mobile carrier in Singapore last month. Investors and analysts are now wondering whether TPG can gain traction in Asia. Credit:Glenn Hunt "They're trying to increase revenue and increase profit through incremental creep. They're hoping people won't notice and will just pay," said online tech entrepreneur Ruslan Kogan, who is now using Kogan Mobile's 30-day billing cycle as a selling point. "There are 28-day and 30-day plans and they're confusing people. It's why when you walk into a supermarket, you now have a product in three different packages and sizes, but there's the 100-gram labelling, to make it easier to compare." Kogan Mobile is among smaller providers, such as Woolworths, Aldi and Boost Mobile, that offer prepaid plans that expire after 30 days. A customer on a $20 prepaid plan with a 30-day billing cycle would need to make 12 payments in a year, totalling $243.33. But on a 28-day cycle, they would need to pay 13 times, costing them an extra $17.38 a year.

But technology expert Angus Kidman, from comparison service Finder, said consumers should consider how much more data and other benefits they may receive with a 28-day plan. "You've got to ask, 'What am I getting?' Depending on the data allowance and quality of signal you're getting, you may end up with a better deal with, say, Amaysim, which has boosted the amount of data you get," he said. "If you look at Kogan, it only runs on the 3G part of the Vodafone network, not the 4G one, so it's intrinsically slower." Mr Kogan responded by saying Kogan Mobile would "very shortly" be moving to the 4G network. The trend towards a 28-day billing cycle has occurred as the percentage of Australians on a SIM-only plan nearly doubled in the year to December 2015, according to Worldpanel ComTech. Some 14 per cent of Australians are now on SIM-only plans.

Pre-paid plans also tend to appeal to customers on tight budgets. The Australian Communications Consumer Action Network said the 28-day billing cycle unfairly impacted on those who relied on cheaper pre-paid plans, adding it was trickier to budget for and track as renewal dates changed. "Consumers need to be aware of this and ensure they have money available in their bank account to pay for a direct debit or money to physically purchase credit when it expires," a spokesman said. "There may also be issues for consumers with setting up direct debits to pay for these plans as some banks have restrictions on how often you can schedule transfers." Joseph Hanlon, editor of comparison website WhistleOut, said he hasn't encountered 28-day billing periods for prepaid mobile plans elsewhere in the world, including the United States, United Kingdom, New Zealand, Canada and Mexico.

He said there were at least 10 other players in the Australian market who used a 30-day billing cycle, including TPG, Aldi and Lebara Mobile. "Expiry periods are just another element to factor into what we consider to be good value, just like call credit and data limits. It would be a mistake to write-off a prepaid plan just because it has a 28-day expiry," he said. "You will pay more over time compared with same-price, 30-day plans, but you might also get more service inclusions to use in that time," he said. "For some people, this is a worthwhile trade-off." All Amaysim customers on "unlimited" plans will be automatically moved to the 28-day billing period. Some have vented their frustrations online. "I hate what they have done with the 28 days thing. They stood out from the others and now they're joining the race to the bottom with the rest of the telco turkeys," wrote a user called Antsey on the Whirlpool forum.

"Optus too has moved to 28 days from 30 days. Over 12 months, this equates to a price rise of nearly one month in extra charges to customers on both carriers ... Sneaky indeed and a clear price rise by any other name," wrote another named Silverbeat. Optus did not directly answer Fairfax Media's questions about why they began offering plans with a 28-day expiry and when the change occurred. A Telstra spokesman said the company offered a variety of pre-paid plans, including the Simplicity offers which can last between 30 days and 180 days depending on the recharge value. A Virgin spokeswoman said the company introduced the 28-day recharge option in November 2015. She said they also increased the amount of data - for example, the $79 plan now offers 8GB instead of 1GB. Vodafone's spokeswoman said it's three prepaid products had expiry periods ranging from seven to 365 days.