Bad Service from Cell C

After numerous attempts to contact the Cell C store at Kollonade as this phone is just ringing without any answer I have phoned customer care. I am due for an upgrade on the 13th of Jan 2016. I was informed by the store in December that I can apply for an additional contract and then just cancel my contract that is due for an upgrade the 13th of Jan 2016. This morning when I phoned in to cancel the contract I was informed that I cannot cancel it as there was an upgrade already done on this contract. I informed them that it's impossible as I did apply for an additional contract as advised by the store and is also billed for this additional contract. But according to them they cannot cancel my first contract because it was an upgrade. Currently they bill me for my old contract and a new contract that is clear when you look at my account. But according to them I cannot cancel the first one as it was an upgrade and not a new contract but I am paying for it as a new contract. Please assist.