Disappearing airtime on Vodacom and Cell C

The results of our latest disappearing airtime test show that when connected to Wi-Fi under identical conditions, Vodacom and Cell C SIMs were charged for out-of-bundle data while MTN and Telkom SIMs were not.

To find out whether “disappearing airtime” is still a real phenomenon in South Africa, we decided to test each of the four main mobile networks – Vodacom, MTN, Cell C, and Telkom.

South African mobile users often complain about their airtime disappearing, and we regularly conduct tests to determine whether airtime is truly depleting on its own.

Previously, this was often the result of out-of-bundle data usage which the smartphone owner was unaware, but sometimes it was a real phenomenon.

For example, MyBroadband previously found that airtime was disappearing on MTN’s network even when mobile data usage was turned off.

Mobile subscriber regulations imposed since these incidents have also required networks to notify customers of out-of-bundle (OOB) data usage and provide them with the option to block out-of-bundle usage.

Our latest disappearing airtime test, which was conducted across Vodacom, MTN, Cell C, and Telkom SIMs, is detailed below.

The test conditions

To determine whether airtime was “disappearing” across any of the mobile networks, MyBroadband placed newly RICA’d prepaid SIMs into four Nokia 5 smartphones.

The smartphones were connected to the same active Wi-Fi connection with identical applications installed, and each was registered to the same Google account.

We also checked if any of the SIMs were subscribed to WASP services via USSD menus. All the SIMs reported they were clean.

Each SIM was then was loaded with R10 airtime at the start of the test.

All settings were left on their default configurations to simulate a real-world usage scenario.

On 1 October 2020, the prepaid SIMs reflected the following airtime balances:

  • Vodacom – R10.00
  • MTN – R10.00
  • Telkom – R10.00
  • Cell C – R10.00

No user actions which would have consumed airtime or data were performed. The smartphones remained powered on and connected to a stable Wi-Fi connection in the same location for the duration of the test.

Airtime balances were recorded regularly and mobile data usage was monitored through the My Data Manager app for Android.

The Telkom SIM was credited with R10 extra of free airtime when we recharged it with airtime – this balance was noted but did not affect the final result.

Airtime depleting on Vodacom and Cell C

The airtime balance on each SIM was recorded on the morning of 2 October and on the morning of 5 October.

This would provide an airtime balance 24 hours after SIM activation, as well as four days after SIM activation.

On 2 October, the airtime balance of each SIM card was as follows:

  • Vodacom – R9.93
  • MTN – R10.00
  • Telkom – R10.00
  • Cell C – R10.00

Note that the Vodacom SIM was the only one to record a drop in its airtime balance over the first day.

By the fourth day, however, this had changed. The airtime balance of each SIM card was as follows on 5 October:

  • Vodacom – R9.77
  • MTN – R10.00
  • Telkom – R10.00
  • Cell C – R9.87

The Cell C SIM was now the second to show symptoms of airtime depletion.

Note that throughout our testing period, the following was observed:

  • No mobile data usage was recorded other than for “OS Services” (detailed below).
  • No out-of-bundle data depletion messages were received.
  • No WASP subscription messages were received.
  • A stable Wi-Fi connection was maintained throughout the test.

Simulating a standard usage scenario where a customer would not expect airtime depletion, the tests had replicated a small but noticeable decline in the airtime balance of two of our SIMs.

The results are summarised below.

Airtime balances over the test period
Network 1 Oct 2 Oct 5 Oct
Vodacom R10.00 R9.93 R9.77
MTN R10.00 R10.00 R10.00
Telkom R10.00 R10.00 R10.00
Cell C R10.00 R10.00 R9.87

OS Services usage when connected to Wi-Fi

It is important to note that our data usage monitoring app observed negligible amounts of mobile data usage over the period despite being connected to Wi-Fi (usually less than 200kB). This measurement was identical across all networks (except for an anomalous Telkom reading) and was attributed entirely to an “OS Services” process on each device.

Telkom was an anomaly, as despite blocking data usage by default when no data bundle is active and maintaining its airtime balance throughout the test, our data monitoring app measured 2.03MB of data usage on the SIM – all of which was also categorised as “OS Services”.

The data monitoring app also showed constant and stable Wi-Fi usage throughout the period of the test for each SIM.

Below is the measured “OS Services” usage for each SIM over the test period (accounting for the entirety of the mobile data usage on each device) compared with the airtime depleted on each SIM:

Network “OS Services” usage Airtime lost
Telkom 2.03MB R0.00
Vodacom 0.2MB R0.23
MTN 0.2MB R0.00
Cell C 0.1MB R0.13

The airtime balance did not deplete on MTN or Telkom – which means that if this OS Services process is the cause of the “disappearing airtime” mentioned above, only Vodacom and Cell C charged for it.

The Telkom and MTN SIMs did not show any decline in airtime balance despite sharing equal or greater “OS Services” data usage measurements, which means that the processes causing airtime to slowly decline on Vodacom and Cell C despite a constant Wi-Fi connection are not prevalent on every mobile network and could be zero-rated on Telkom and MTN.


Vodacom responds

Vodacom said it charged the SIM we tested for out-of-bundle data usage, stating this was possible if a device was connected to a poor-quality Wi-Fi connection.

“What transpired with this specific Vodacom Prepaid SIM is that, whenever the device handed over to a cellular connection, OOB (out of bundle) rates applied on the SIM,” Vodacom said.

“Our OOB block implementation is in line with the ICASA regulations. The regulation states that no OOB charges are to be applied by default once a data bundle is depleted,” the network added.

“If this is a new prepaid SIM which attempts to use data without the purchase of a data bundle, OOB usage will be applied. We stop applying OOB by default after the depletion of an active data bundle.”

“Some of our customers prefer to manage OOB charges themselves and so Vodacom has also catered for this through the creation of the Data Limit lock service, which allows customers to set their limit to zero, should they not want to be charged any out of bundle rates or set a higher limit,” it said.

Vodacom did not state which applications were responsible for this out-of-bundle data usage.


Cell C responds

Cell C also said this airtime depletion was due to out-of-bundle data usage.

“We can confirm that there were legitimate charge requests coming through from the network. Looking at the usage, it is background application from the device, the only possible explanation is due to the connection on Wi-Fi dropping that it used the mobile data,” Cell C said.

“The subscriber would not get any out of bundle notifications as these would be generated when a subscriber/SIM has a data bundle loaded and the bundle depletion reaches defined thresholds.”

Cell C did not state which applications were responsible for this out-of-bundle data usage.


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Disappearing airtime on Vodacom and Cell C