Vodacom dishonesty

Such a dishonest service provider to not disclose to me, a pensioner, that if I upgrade my phone with the upgrade deal they sent me per email (I didn't ask to upgrade my phone) I would have to pay for 2 handsets for 3 months. Vodacom just debited my account with the additional costs, without authorisation and refuse to credit my account. If Vodacom had advised me upfront of the additional charges I would not have upgraded my phone and waited 3 months. On top of that, they have charged me for a full month in June even though the original contract end date is 8 June! They steadfastly refuse to credit my account and continue to debit my banking with increased amounts I have not agreed to.