Being charged for a phone I did not order

I ordered an iPhone 7 on line from Telkom on 28th June. On 1st July the monthly installment of R639 went off my account and I received the phone on the 10th of July. On the 13th of July the courier arrived with another phone. I told him it was a mistake and he said just sign for it and let Telkom know so they can arrange for the courier company to collect it. Which I did. After 2 weeks they still hadn't collected so I called again and they eventually collected on the 8th of August. In the meantime I received a statement charging me for both phones. I called to get them to rectify this and the lady confirmed it will be cancelled I asked where my proof was of this and she said there is none, I must just keep checking my bill to see if it has changed. When it had not I called again. The man I spoke to told me to eft the amount I actually owe and Telkom will deduct the money on the statement and reverse it again once the cancellation is activated. Well I called my bank to reverse the money because to date Telkom has not rectified this and I am now getting threats of being disconnected, being black listed and handed over to attorneys. I have called another 3 times. Being told I need to fill in a cancellation form which takes 21 days to kick in. Now it is funny how they are going to cut off the services for the phone I am using and paying for, but they are not threatening to disconnect the phone I do not have and am not paying for.