Billed for Cancelled contract

On about the 27th February I gave Cell C a months notice that I will be terminating my contract with.<br> They said it would be cancelled on 27th March 2014 and my reference number is ***<br> I have ported my number to Vodacom but on Wednesday 1st April I had R92.00 taken from my account<br> reference SP ***<br> I know Cell C has a cash crunch but taking money they're not entitled to does not help<br> ***