Contract not cancelled

I am very disappointed with MTN. I renewed my contract online and I had financial constraints when the device came unfortunately could not take the contract as soon as I received the device I contacted the CC and advised them of my situation and was advised to return the device to the nearest MTN Branch and I did return it within 7 days to MTN at Ferndale On MAIN on the 27th of June. Ref Number IRMS***.

I sent an email and requested cancellation on the contract but I did not receive any feedback I sent again an email on the 12th of July detailing all the events and why I want to cancel the device and still there was no response.

On the 2nd of September R571 was deducted from my FNB account. I called MTN no response, I went on Facebook and queried this and got a reference number REQ*** till now there hasn't been any communication.

How do you deduct money from someone who does not have the device.???? what exactly am I paying for?????? If I get a contract from MTN am I not allowed to cancel within the days as per the agreement?????????

Can someone please sort this out for me as i will not allow MTN to deduct money from my acc for something that i do not owe.