Many smartphone users have complained about airtime and mobile data disappearing from their accounts, despite not accessing the Internet or apps.

Apps running in the background, which are consuming data, are a common culprit.

Additionally, features such as Wi-Fi Assist can cause you to automatically switch to mobile data when you have a poor Wi-Fi connection.

To test if data or airtime “disappearing” was a genuine issue on local mobile networks, MyBroadband bought and registered new prepaid SIMs from MTN, Vodacom, Cell C, and Telkom, and conducted an investigation.

New SIMs

Each prepaid SIM was loaded with a small amount of airtime via an online banking app and placed in a Samsung Galaxy S7 smartphone.

The smartphones were connected to the same Wi-Fi connection and the “mobile data” usage option in Android on all four devices was turned off.

All settings similar to Wi-Fi Assist or dynamic network switching were also disabled, as we wanted to ensure the smartphones did not establish a mobile data connection during the test.

On 11 July 2017, the prepaid SIM cards were installed in the smartphones and had the following airtime balances:

Vodacom – R12.00

– R12.00 MTN – R10.00

– R10.00 Telkom – R10.00

– R10.00 Cell C – R10.00

No user actions which would have consumed airtime or data were performed. The smartphones remained powered on with their mobile data switched off, and their Wi-Fi connections on, for a period of 11 days.

Airtime balances were recorded regularly throughout the test.

Disappearing airtime

What happened during the test truly surprised us. While the airtime balances on the Vodacom, Telkom, and Cell C SIMs remained the same throughout the test, the airtime balance on the MTN SIM steadily decreased.

The MTN number also received daily SMSs from MTN warning that it was using out-of-bundle data – despite the mobile data option in Android being turned off.

The data usage monitor on the smartphone further showed that 0 bytes of mobile data had been used in the last 30 days.

The airtime balance on the MTN number exhibited strange behaviour, and would occasionally increase slightly before continuing to decrease.

The airtime balance of the MTN SIM decreased to:

R6.38 by 17 July

R4.60 by 21 July

The balances for each prepaid SIM on 21 July were:

Vodacom – R12.00

– R12.00 MTN – R4.60

– R4.60 Telkom – R10.00

– R10.00 Cell C – R10.00

After we noticed the disappearing airtime on the prepaid MTN SIM, we went to an MTN store, purchased another new prepaid SIM, and installed it in a different smartphone, a Huawei P8.

The mobile data option on the Huawei was turned off and the SIM was loaded with R15.00 airtime on 16 July.

The new MTN SIM displayed the same behaviour as the previous SIM, and its airtime balance slowly decreased – despite no mobile data being used.

Screenshots of the data consumption messages sent by MTN and the Samsung’s data usage monitor are below.

Your LTE connection uses data – MTN

MyBroadband presented its findings to MTN, which acknowledged that the data depletion was genuine.

It said the reason for the data usage, which caused the airtime balance to drop, was due to the devices establishing an LTE network connection.

The LTE connection charged a minimum tariff, despite the device’s mobile data being turned off.

“MTN would like to note that even though data was switched off, the smart devices used in the test consumed data when connecting to the LTE network, this is how LTE works,” said MTN.

“We can confirm that the depletion was due to Internet data traffic being channelled directly to the handset via LTE technology.”

“LTE is an always-connected technology, and as a result of LTE standards, any compatible device connecting to the LTE network receives an IP address.”

According to MTN, the traffic generated is valid data traffic and the sessions incur a minimum data charge of 3c, a tariff the company filed with ICASA.

“These charges only occur when an LTE device, containing an LTE SIM card, is in an LTE coverage area. This affects less than 3% of our customer base and does not occur during any 3G or Edge data sessions,” said MTN.

MTN said it was not aware that other mobile networks were zero-rating the LTE sessions, and said it would implement a solution in the near future.

“As a matter of priority, we are going to adjust our tariffs and align our data charging in LTE with our competitors. This will be implemented within the next 30 days,” said MTN.