cell phone upgrade

I upgraded with cell c last month, I received the phone on the 28 September 2015. first the sim card slot was not working and I reported the issue to cell c then they said they would send a courier to collect the phone which never ever arrived, I then tried the sim card again which ended up working but not 100%. then after 2 weeks I called to activate the sim card which was never activated and did a sim swap this process took a week and I was told everyday that it would take 24 hours. today the sim swap took place after waiting so long. now this new sim does not work in the new phone it only works in the old phone. I called cell c today to report the problem then the phone worked, after 10 minutes the phone again started saying no network even though the sim is inserted. what is going on with cell c. I really need help with this as I am very tired now.