Very bad service by Vodacom

I upgrated my phone contract on the 1 June 2019 as i was told that is due and for the new contract im supposed to pay R499, bu to my suprise they started debiting R757 without any communication with me or checking on my concern if i will afford to pay that ammount. After finding out that they are debiting more i visited the nearest outlet and i was told that im paying for 2 contracts. What on earth can i take a contract while the other 1 is still existing. i cant afford two contracts and the way it was blind folded to take another contract i feel like blocking my bank accont because Vodacom was dishonest to me. With other service provider they continue withthe previous contract until it ends then they start with the new 1 for 24 months. What is so special about Vodacom to rigg people for the little money while the cost of living is this high. My name is Andzani Nyambi cell number ***