**Editor's Note: Click here for a recap of some of the worst cases of bill shock of all time.**
A popular $59 plan has been causing phone users to suffer from major bill shock as they spend significantly more than expected on their phone bills.
This expensive shock costs Aussies about $557 million every year, according to new research by Macquarie University, and this population spends about 50 percent more on phone bills than expected each month, Smarthouse reported.
The research examined more than 200 mobile phone bills, and it shows that about 40 percent of phone users on contracts deal with bill shock. Also, people signing up for $129 or $60 plans are left just as susceptible to the shock as those who sign up for cheaper plans.
People on $129 plans experienced the highest bill shock ($155.58 worth), followed by those on $59 plans, $60 plans and $49 plans. The major causes of high phone bills are "standard" call charges, excess Internet data charges and international calls, according to the research.
"Recent changes adopted by the industry since this bill analysis are a step in the right direction," said Dr. David Gray, senior lecturer in marketing from Macquarie University. "But the bills we've viewed even in the past few weeks still left us scratching our heads."
Gray added that the concept of "included value" in mobile plans needs to be more clearly communicated to the customer.
There have also been warnings that a new 4G LTE network may cause a new round of bill shock.
Next year, telecom companies in Australia will be required by law to send user alerts no later than 48 hours after users hit thresholds of 50, 85 and 100 percent on their plans, and some companies already do so. The European Union already requires such alerts and U.S. wireless companies are voluntarily implementing similar procedures.