Cell C refusing to change device/cancel contract

Following my complaint yesterday about Cell C not wanting to change my iPhone 5s that I have only had for 7 working days after an upgrade to an iPhone 6s, today a guy called Patrick called me and I asked him that they should cancel my contract altogether so I can pursue a different network for a contract iPhone 6s and Cell C is also refusing to do that. I do not understand why a loyal customer has to be treated like this. Reality is that I do not want this phone and if Cell C is failing to either change my phone can they please cancel the contract that I have with them and take their device back! I'm not gonna pay for a phone that I do not want. If the two options do not work for Cell C, I'm gonna stop paying for this device!