Requested for line to be blacklisted but still wor

On the 18.03.2015, I requested for my sim and phone to be blocked as it has been lost. To my surprise when I call it, its ringing, when I call the call centre, they just pick up the line, put me on hold and then miraculously the phone cuts...<br> <br> Can someone please do their jobs as they will be telling me that I owe them thousands as they failed to block this line.