CANCELLATION NOT DONE

I recently complained about a contract I wanted to cancel with Virgin Mobile due to the phone not being available. Eventually they did agree to cancel the contract with effect from 12/09/2015 and I received confirmation of this in writing from Andrew Nhlapo. I have now received a bill for a higher contract I did not take out and a phone that I do not have. I was also advised that no contract was cancelled. I want the contract that I initially had, to be cancelled with effect from 12/09/2015 as confirmed and a credit for the higher contract that I did not take out to be done immediately. I am supposed to be on pay as you go from 12/09/2015.