Unhappy customer

I’m really not happy with what vodacom did to me, on their app it showed an amount that i had to pay, i paid and after i was told that i have to pay R600 extra but it didn’t appear on the app, and my outgoing calls were 🚫 blocked and I called customer care, they said there was another invoice separately from the one i have seen. And I don’t understand why 2 separate invoices for 1 account and i am the one paying the account. Please help,