I was given the incorrect information, now I need to pay!!!

i there, I called your office on 23 May 2018 to request settlement amount for my Vodacom account, I did not get the gentlemen's name but he gave me a discount as and said of I settle the same day I need to pay R2200 and the account will be paid up and closed. I repeatedly asked to to reconfirm the amount to make sure I'm paying the exact amount because I needed this debt to settled. (please see proof of payment attached) on the 29 May 2018 I received an SMS stating I have a outstanding balance of R447. 38. I called your office to find out and was told that I was given the incorrect settlement amount and the costs not paid has now grew to this. This is not my fault and unacceptable as I paid what I was told to pay. I called twice and was promised a call back but this did not happen. This is bad customer service unacceptable Before you know it this amount is huge but I will not be liable to pay this. All I want is for this account to be settled and closed and a paid up letter to be sent to this email address I thought the account would be closed by now seeing that I paid it on the 23 May already