Unjustified Debit Order

I took out a contract in May with two handsets for my children R299 each per month with the option to top up. R598 came off my account on the 13th of May and again on the 28th of June (not 1st as I requested), and today R1298.88 were debited. I phoned and I was assured I will be phoned back by Vodacom before 3pm today. Still no phone call and no statement from Vodacom to justify the amount. As if we aren't busy enough. Vodacom, if you don't sort this out within 24 hours, I am cancelling my contract. Very disappointed.