Still billed for cancelled contract

I obtained a data contract with Vodacom in April 2013 which expired in April 2015. Included in this contract was a Lenovo Laptop. In April 2015 I contacted Vodacom to cancel the contract and return the number used in the contract to pay as you go.<br> <br> Today while going through my Vodacom Accounts I see that I have been billed R79 per month from May 2015 for a contract that had been cancelled in April 2015. <br> <br> I did not notice this as the Postal strike delayed all account and I only now had time to go through many months of accounts received in early 2016.<br> <br> Bear in mind that I had a data contract from 2008 to 2011 and 2011 to 2013 both of whom I cancelled and both of whom were promptly cancelled and the numbers either deleted or turned into pay as you go numbers. I have had no problems doing this in the past.<br> <br> I was able to cancel the contact as of 31 March 2016, but what about the charges from May 2015 to current? Will these charges be returned to me? This is a small amount, but come on guys why do you need to take money when the contract is cancelled?<br> <br> Please contact me so we can resolve the issue, your customers service will be unable to do this.