Optus is keeping tabs on continuous mobile data sessions in six-hour or 100 MB increments to meet its Telecommunications Consumer Protection (TCP) code obligations.
The carrier is the second of Australia's big three to reveal how it accounts for data usage in order to warn customers when they reach 50 percent and 85 percent of their quota limits.
Such warnings are mandatory for large telcos under a section of the TCP that comes into effect on September 1 this year.
Telstra is accounting for long mobile data sessions in increments of 117 MB, as revealed yesterday by iTnews, explaining why customers had started seeing repeated references to the number in their bills.
While Telstra's system configuration changes are fairly recent, Optus started changing its systems to implement data usage alerts "in late 2011", before bringing the alerts online in September last year, a spokeswoman for the telco told iTnews.
"To determine customer usage, the general rule is we cut data at the end of the session, every six hours or when a 100 MB threshold has been reached – whichever comes first," the Optus spokeswoman said.
Vodafone Hutchison Australia (VHA) appears to be the only one of the three major telcos which didn't have to make any system configuration changes to introduce data usage alerts.
Vodafone previously offered a balance alerts system which is being replaced by the newer usage alerts.
"Our billing system didn't require any work arounds to deliver the [new usage alert] service," a VHA spokeswoman told iTnews.
VHA did not reveal in what increments its systems look at mobile data usage.
While "large providers" had until September 1 this year to make data usage alerts possible, smaller providers have to comply with the same obligations by the start of September 2014.
The Communications Alliance yesterday published an industry guidance note on the implementation of spend management alerts ahead of both deadlines, though it seemed most carriers — large and small — were not leaving it until the last minute to comply.
Telcos mostly passed their first major compliance check on other parts of the TCP, which set out rules for complaint handling.
The Australian Communications and Media Authority yesterday said Telstra, Optus and VHA demonstrated a "high level of compliance" in checks involving a sample of about 200 customer complaints each.