******* billing on credit card for no reason

Good day,<br> <br> I got a notification that I was billed and also for no reason. I was subscribed to Office 365 but cancelled it in March, and then got billed the extra amount last month, which for some reason showed up today? <br> <br> Please explain as to why this is and how I can get it reversed, as this is completely against anything that I signed up for.<br> <br> Please see the copied an pasted info from my account below:<br> <br> 29/04/2015 Office 365 Personal R-10,50 <br>