Cell C is refusing to exchange my damaged iPhone 6

I recently bought two iPhone 6, gold & silver 16GB on contract at The Glen Mall first week in June 2015. The Silver iPhone has no issues. The gold iPhone started freezing within 4 days of purchase so I took it back within 7 days. However, I've been calling Cell C to find out the progress of my phone and I've been getting different stories. Last week Friday I called and spoke to a lady sales person and she told me that the RMA has been approved and she's going to order a new phone this past Monday, and it was going to be available in store for me to collect this week Thursday or Friday, because they didn't have any stock. Today when I called I'm told that they're waiting feedback from the Repairs. I don't know who's telling the truth or who to believe. It's almost a month and I still don't have my phone. If Cell C doesn't resolve this matter by next week Monday (6 July 2015) which will be more than a month, I would like to cancel the contract due to poor service delivery on damaged goods.