Airtime disappearing.......Vodacom you are at it again!

I renewed my contract with Vodacom in April 2018. Since then all my airtime, 250 minutes gets 'USED' by 6th of the month! This is impossible considering in the past 10 years, I have never gone over this limit. I requested an itemized bill and when I queried it, as it was clearly wrong, no one ever came back to me. Instead got an SMS saying that the matter was resolved! It is clearly not resolved. It is the 6th of June and guess what? My 250 minutes ran out again today. That means that for the past 4.5 days, I have been on the phone for over 45 minutes a day, which is IMPOSSIBLE! Vodacom are clearly billing me incorrectly or *****ing my airtime. In the past they stole my data and had to give it back, now their attention seems to be my airtime! The problem is that no one ever takes responsibility. I am told to get an itemized bill which I do, then someone else forwards it to another department to look into. You are not given a name or reference and then they just happily close the call! I have been a Vodacom customer since the 1980's and am so sorry that I have renewed with them again - biggest mistake of my life as they are absolutely not interested in their loyal clients and have now proved two months in a row that they are wiping out my airtime! There is a word for this - theft!