Mtn
Still getting bills after contract cancelled

In March of this year I moved to Australia leaving my cell phone contracts behind to run their contracted term to the end of August.
Anticipating a notice period I contacted MTN in May asking how to go about cancelling my contracts.
It took them a month to respond with "Please note that to cancel we only need 90-30 days. You can call us at 808 or email us once decided".
I then specifically asked for the contract to be cancelled whereafter I received confirmation as follows:
"Thank you for your email.
Please note that contract number 083xxx/083xxx will be cancelled on 2013-08-16 as per expiry date. Kindly contact us before the expiry date If you still wish to keep the number on prepaid."
Excellent news. I requested the number remain on prepaid and then got this bizarre response:
"... Kindly contact us after the expiry date of the contract to cancel and migrate the contract to prepaid. The expiry date is 2013-08-30 ."
I responded again to set out the flow of discussions so far and re-confirm cancellation.
Despite this I continue to receive bills. Can someone now please resolve this once and for all and refund monies recently debited to my account.
Very Frustrated!