Paying for a phone I don't have

I am being charged for a phone that I cancelled the order on,was told I could not cancel the order and was then told by customer care to simply refuse to accept the phone when being delivered. I would be charged R150 for the courier, which I was okay with, and the order would be cancelled. For months I have been sent charged for this non existent phone despite countless emails, Facebook posts and calls.....now they are threatening my credit...after years of being with these guys and having no problems. Really really bad service.