Airtime used for data charges with data bundle available

<p>This is the second week running whereby I have bought a data bundle and no data is being used but the "remaining" airtime is being depleted. On Thursday morning last week, i had 300mb of data and R32 of airtime. I made 1 call which was less than a minute on the day and used the internet/social media apps on my phone alot.by 7pm of the same day i had R0.00 airtime and 258mb of data remaining. Why is my airtime being deducted for data and not from my data bundle?? this is really pathetic service. previously i had the same issue and was told that there was a problem with their system and this would be resolved in 48 hours which it was, now the same thing is happening! this is really frustrating, knowiing you have data and airtime but the airtime is being used for data charges!! please resolve these issues you are having and i would like to have answers on this problem</p>