Bad service from cell c

I had purchased a double deal contact from Cell c in store. I went back to the store within the first 7 days and had told them that the Bluetooth function on the phone was not working on the phone, they then advised that they would get the technician to contact me as they could not solve the issue. About a week later the technicians still have not contacted me and I informed the store about that, eventually when they contacted me they gave me settings to try via WhatsApp. I did what was asked the Bluetooth function then worked however after a hour or two it went back to not functioning and I tried the settings twice again but still it was not working. I informed the technician and they said they will get someone to call me however from this point forward they would not contact me unless I reminded them to contact me and then contact was made, I was told a supervisor will contact me but then never does. I then contacted the store again, that is when they explained that I would have to send my phone to Cell C technicians/repair center I then explained that I do not want the phone to be opened up or things replaced they said that they won't. I received a call from the store last week stating that my phone has arrived and is ready for collection, upon collection I was told that the phone was opened and components was removed and replaced and that I needed to use the phone and if the problem persists I can then only receive a new/replacement device that was the policy. I then explained that I understand that is the policy however I was sold a defect device and I reported the problem within the 7 day period and if components needed to be taken out and replaced then the phone was faulty from the start and is now no longer a new device, I would like a new Device. I was told that can not happen even though this is not longer a new device as it was open I need to use it,no one contacted me from the repair center to explain what the problem could be or to ask permission to open the device it was just opened and sent back. Could this matter please be seen to as I do not want that device back I would like a new one, I am paying for a device I can not use or does not have in my possession.