Why data disappears on Vodacom and Cell C’s networks

A combination of out-of-bundle (OOB) data usage policies and LTE technology is to blame for data disappearing from Vodacom and Cell C SIMs even when their mobile data is turned off.

That is according to feedback from Cell C chief technology officer Schalk Visser in response to a recent MyBroadband test which showed that Cell C and Vodacom SIMs lost airtime even when turned off.

It is important to note that this was not related to fraudulent billing by rogue Wireless Access Service Providers (Wasps), which sign up customers to expensive content services without their consent, stealing large amounts of airtime.

MyBroadband ensured the SIMs were not subscribed to any such services during our testing, purchased data and airtime for all SIMs and then disabled mobile data. We did nothing with the phones but check their remaining airtime over USSD.

After two weeks, Cell C and Vodacom had lost 1.07MB and 0.19MB of data, respectively, while Telkom and MTN’s data and airtime were untouched.

Although Cell C and Vodacom lost small amounts of data, their value could amount to millions of rand every month when multiplying the figures over the operators’ entire subscriber bases.

MyBroadband has conducted several similar tests over the past few years and always found at least one or two mobile networks were consuming data while mobile data was turned off.

Telkom was the only network that never consumed data under our test conditions.

According to ICASA’s End-User Service and Subscriber Charter, OOB mobile data usage must generally be an opt-in service in South Africa.

However, networks can choose to only disable OOB data depletion once a bundle has been purchased and depleted.

They can also continue billing customers out-of-bundle, provided the OOB rate is equal to their in-bundle rate.

Visser said that most networks had chosen to allow OOB charging for data by default, with the onus being on the subscriber to initiate a change to prevent this.

Telkom is the only network that disables OOB usage by default, regardless of whether a user has bought a bundle or not.

Vodacom and Cell C require customers to proactively disable out-of-bundle usage via their USSD menus, while MTN disables OOB after a customer has bought and depleted a bundle.

But the question remained — why was data being used when it was completely disabled?

Visser explained this was down to the different methodology in which a mobile device connected to LTE networks, as opposed to the older 2G and 3G networks.

“For 2G/3G, voice and data are provided by different elements in the network — the Circuit Switched (CS) network for voice and Packet Switched (PS) network for data,” he said.

“Should the user deactivate mobile data while attached to the 2G/3G network, the mobile [device] will still be attached to the CS network to allow for voice services to continue. In this case, there will be no data usage.”

But with LTE, mobile devices attach to the same network elements for both voice and data.

That is defined in the LTE standards set by the global mobile telecommunications industry’s 3rd Generation Partnership Project, which requires that LTE have an “always on” connection.

“When a user deactivates mobile data while attached to LTE, the connection to the LTE network cannot be terminated as this will also terminate any possibility to make voice calls.”

“This would be true for Voice over LTE (VoLTE) or where VoLTE is not supported or deactivated,” stated Visser.

Due to the “always on” requirement, LTE networks send small packets of data to devices even when their mobile data is switched off.

Visser said it was usually only a few fractions of a kilobyte of data sent in these instances.

“The only way to completely prevent any data usage is to activate airplane mode, but this will also deactivate voice calls, SMS and USSD,” he added.

Schalk Visser, Cell C Chief Technology Officer
Schalk Visser, Cell C Chief Technology Officer

A Vodacom spokesperson said that stopping all OOB services would “negatively impact customer experience” and the growing demand for communications.

“It is important to note that active customers on our network, for the vast majority, purchase a data bundle using their available airtime,” the spokesperson said.

It is interesting to note that during a 2020 test where we tested OOB airtime depletion and did not buy data bundles, we found MTN consuming data, but not Telkom or Vodacom.

Another interesting point is that the issue seems to occur only on Android-powered smartphones, not iPhones running Apple’s iOS.

Previous tests by MyBroadband showed that the small packets of data sent while mobile data was disabled were due to connections to Google services such as “connectivitycheck.gstatic.com” and traffic to resources that belong to Amazon, HP, Time Warner Cable, Verizon, China Telecom, and MIT.

The table below summarises which networks consumed data in our latest test and whether they allow OOB billing by default.

Data depletion on LTE device while mobile data is turned off
OOB usage allowed by default Data usage after bundle purchase End result
Vodacom Yes Yes Data used
MTN Yes No, blocked by MTN No data used
Telkom No, blocked by Telkom No change from default No data used
Cell C Yes Yes Data used

Now read: Cell C says MTN’s proposed Telkom acquisition must be handled with care

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Why data disappears on Vodacom and Cell C’s networks