Unkown Fees they want me to pay

Before settling my Virgin active account I spoke to one of the call center consultants regarding the settlement value and he voiced it out on me telephonically and I insisted on something in writing he said to me I will only get that once I have settled my account in full. So I then verified the amount to be paid and flagged to him when I am planning to pay and he assured me that the amount will the one he told me about over the phone. So I Paid the amount he told me over the phone and now to the shock of my life I am getting a settlement letter which I requested before making any payment stating that i need to pay R144. For what because I was given money telephonically by the staff of the same company whom refused to give it in writing, now they are doing it in writing and want me to pay it. I am very sorry I am not going to pay that, since I took initiative of requesting the full settlement from them and they just did not want to give it to me. They will have to settle it. Go back and check telephone recordings and we can talk.