upgrade

My wife done a upgrade on her tablet, the same way we have always done our upgrades. This is the 2nd month that vodacom has dubbel billed us on the tablet. The 3g laptop installment of R240 gets taken off twice on 1 bill, I phoned vodacom call centre they tell me to call the Voda shop where I done the upgrade, the shop tells me to phone the call centre, nobody can give me a answer. R480 is just gone for no reason