Incorrect Device Received

I purchased a Huawei P8 Lite cell phone at CNA Mall@Carnival on Sunday the 15th of April 2018. After a lot of research I noted that the Huawei P8 Lite 2017 has Android 7 whereas the 2015 model only has Android 5. I found that CNA has one of the better prices on the Huawei P8 Lite 2017 which was R2 999 as per their website. Upon entering the CNA, I saw that there is a Huawei P8 Lite that is marked down from R2 999 to R2 500. I then jumped at the opportunity and purchased the phone. The packaging was opened since I was advised that this has to be done in order to check if the phone was working, which is understandable. Upon getting home, I started running updates on the phone and saw that the Andriod version was 5 and not 7. I realised that this was in fact the 2015 model and not the 2017 model. Since there was no indication on the label with the price, of which model it was, it was logical to assume that this is the Huawei P8 Lite 2017 since it's normal price was advertised as R2 999. I was so disappointed because this is not what I believed I purchased and it is not an immaterial amount to me. I could have then purchased the correct phone elsewhere for a fraction more. Upon trying to phone Edcon's customer resolution centre this afternoon, I tried to get through 10 times if not more. Eventually someone answered the phone and after explaining the situation the call was ended by the consultant. I then tried to get through again about 5 times but to no avail. I feel that I have to receive the correct phone from CNA even if I have to pay the additional R500 but the situation is undoubtedly unfair towards me as the consumer. I have had an account with Edcon since 2006 and I am a loyal customer. Surely that should also count for something.