Overcharged and contract migration without knowing

I noticed that my premium has increased for a few months and I was not aware until I went to enquire at the Vodacom store in Cresta Mall. I was informed that my contract has been upgraded/migrated and I am not aware of this. I have contacted the number (***) I was provided with by the store and was sent from post to pillar. These are your other numbers that I contacted to find out what is actually happening - *** and 082 135. Please put me back to the initial contract that I am aware of or alternatively cancel the contract. Should you decide to put me back to the old contract that I am aware of, please refund all the money that I was overcharged, i.e. the difference between New and old contracts for the months paid.