Vodacom Direct called me for an upgrade without explaining that there is extra costs.

I was contacted by Vodacom Direct call center to tell me that I can upgrade my phone and By doing so I will reduce my costs as well as get an additional 1GB of data per month. I agreed and then I found that by Bill was R1230.39 in stead of what was confirmed. I went to Vodacom in Somerset Mall where the Consultant told me that the issue is that the extra charged on my account for my previous handset that I did not finished payment for. (About 4 months of installments). I asked him how is it possible to upgrade with outstanding funds. He said that I need to contact Vodacom Direct as they did the upgrade. I did call and spoke to Nicome Ref number 19373 on the 30/11/2018 and asked her that she must have a look on their recordings as I know I would not have agreed to an upgrade if there was outstanding funds to be paid . She said that she will be come back to me withing 3 to 5 days . I heard nothing from them and had to call again today 11/12/2018 and spoke to Nokotula Bilima Ref 19373 who told me that they have investigated the matter and told me something to the affect that with the upgrade all current payments will still apply. I understand that as my contract consist of additional data pmt and a 10GB MBB , but under no circumstances was there said that I need to understand that by upgrading now I will incur exstra costs for outstanding contract fees that is outstanding. I asked her to send me the recording to listen to it and she said that I need to go to the closest Vodacom Shop and they will mail the recording there and I need to go and listen to it there. I did go back t Vodacom Somerset Mall and let them call the Vodacom Direct to mail the recording . I then asked them to mail it to me , which they also declined and said that I have to listen to the recording there. I found it very unfair as I need to now listen to a recording with a Shop full of people that is talking as the mall is busy. I listened to the recording and it started with Chris introducing himself and stated that I am paying to much for my contract R690 and that he can reduce it to R179 pm . I asked if I would then only pay for the contract and not get a new handset. He confirmed and asked if I want a new handset. I agreed and he asked what do I currently have . I said a Samsung S7 and he said that I could look at the s8 and he just want to work out what that would cost me. He came back and said that the same package Smart S contract with an additional 1GB pm will now cost me R609 per month and iso. the R690 that I am currently paying= almost a R100 saving (His Words) . He reconfirmed "Moving forward R609 per month for the Smart S package and it will replace the R690 from next month. " then he confirmed the terms and conditions and do I agree on the R609 plus a once off R150 Admin costs. Then the verify'er ask if I was helped by friendly consultant and I rep**** "Yes" he asked ,if I understand that the new phone and contract is a New Smart S Contract will be R609 per month for 24 Months and I said "Yes " again. They thanked me and the call ended. My issue is I did not agree to any additional charges over and above the R609 + once off admin fee of R150. Vodacom representatives also did not tell me that I still owe them money and that they will still charge over and above the R609 per month. I feel that I was mislead by not informing me and because they have a debit order on your account , just took the exstra costs without my knowledge. Could somebody give me advise as to what my next step is as this is unacceptable. Regards Jannie