Vodacom using my data and then my airtime

<p>I usually receive a message when my data is low but it hasnt been the first time this happened where when my data is complete, Vodacom used my airtime. This is the problem. They usually send me a message to say its 15mb left but this time im fed up. I am a loyal vodacom customer and have been told countless times to change by my family but this time im seriously considering because im fed up. Now where must i get the airtime again i have to wait til end of the month. Thanks for nothing vodacom</p>