being shunted left right and centre

My invoice received this month is less my hand set amount. My contract only expires in August so it should still be billed to me. However, despite the numerous people I have spoken to this morning, not one of them can advise why this is so. Not only am I shunted from pillar to post regarding this matter, the staff transfer me to another person and I end up sitting on hold for 30mins until eventually the call drops, I am almost certain this is a deliberate attempt by the staff to get rid of my call. I then have to phone back and go through the entire sordid process again, and explain my situation again to numerous individuals who just have no CLUE. Incredibly frustrating and so unnecessary. I am putting this on record, should Vodacom decide to double bill me next month because their staff are ***********!