Data dissapear

I am very very upset about Vodacom *****ing Data. My data just disappears at times. If I do certain actions I get the message that I have insufficient funds to do the transaction while I have more than enough funds (date) to do the transaction. What is the problem with your data. I cant put my mobile data on as 5 min later , all the data is gone. I am not stupid and know how to check for apps *****ing data, it is not the case. You are *****ing from us.