miscommunication on contract

I went for an upgrade the 1 may and the lady that did it for me informed me that my new handsets instalments would only go off the 27 June however I was billed on the 27 may which I did not expect because I never got a statement to say how much I have to pay nor did I get my airtime or data that was promised on the new phone. I was only expecting my normal payment to be deducted as stated by the lady that helped me. I went in the store and spoke to them and they saw that they were wrong however I am still waiting for them to get back to me as to what I must do regarding payment because I never had that full amount.. it has been a week now and i still haven't received a response. I am now being charged a penalty fee by vodacom and bank charges which I think is really unfair because its their fault and I want to be refunded.. I just want answers. I am willing to pay my normal installment that was said to go off 27 May and my new one the 27 June