calls made on blocked cell nr

My cell nr was requested to be blocked meaning deactivate the cell nr on the 2 May 2015. Well the sim was unblocked etc. And calls was made by whomever... a dispute was lodged and declined as per the service provider it wasnt closed etc. So i have wasted my time going to the Kimberley branch by reporting and requesting a block. So each month i have to pay for someone else making calls and downloads.