Strange data use uncovered on Telkom and Cell C
Out-of-bundle setting testing by MyBroadband uncovered a strange anomaly where Cell C and Telkom seem to prevent users from consuming their entire data bundle.
Out-of-bundle settings determine what happens to your data connectivity when you run out of data.
There are typically two options:
- Use airtime when you run out of data.
- Cut the connection until more data is loaded.
Vodacom and Cell C also make it possible for subscribers to limit how much airtime can be used.
The airtime limit lock on Vodacom can be set to any value, while the limit on Cell C is only adjustable in R10 increments.
This limit is useful in an emergency to allow subscribers to still connect to the Internet when they run out of data without the risk of bill shock.
To establish whether these settings work as expected, we loaded airtime and data on SIMs from each mobile operator and put it to the test.
The out-of-bundle settings were applied to limit the use of airtime to a small amount or altogether disable the use of airtime.
The Vodacom SIM was set to allow only R1 of airtime use for data, while Cell C was set to R10.
MTN and Telkom SIMs were set to block all airtime from being used as data.
The SIMs were then used to browse the Internet and stream YouTube videos until connectivity was lost.
The out-of-bundle settings worked as expected for all the SIMs.
With Vodacom and Cell C, airtime use was limited to R1 and R10, respectively – in line with the setting. Telkom and MTN cut off connectivity when all data bundles were depleted.
The table below provides an overview of the test results.
| Out-of-Bundle Settings | |||
| Network |
Out-of-Bundle settings | Settings used |
Airtime Used |
| Vodacom | On/Off/Any monetary limit | Allow R1.00 use | R1.00 |
| MTN | On/Off | No Airtime Use | R0.00 |
| Telkom | On/Off | No Airtime Use | R0.00 |
| Cell C | On/Off/R10 interval limit | Allow R10.00 use | R10.00 |
While the settings worked as expected, Cell C and Telkom displayed concerning behaviour during the test.
At the end of the Cell C testing, it cut off network connectivity after the R10 airtime was used up. However, according to the Cell C balance check, there was still 0.98MB of data left.
No matter what we tried, the phone would not make a data connection using this left-over data.
When we loaded more data, this left-over data was added to the newly loaded amount, but when repeating the test, the same thing happened, leaving 0.49MB this time.
Telkom showed similar behaviour, leaving 7.86MB on one streaming bundle. As soon as we loaded new data, the old bundles suddenly showed no data left.
A possible explanation is that the Telkom app used for checking data balances was slow to update and only noted the depletion of the previous bundle when a new one was loaded.
It is, however, of concern that it may be possible for a user to consume airtime when it still looks like they have data left in their account.
Now read: Best mobile network in South Africa in 2021 — including city rankings
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