Debited even though we cancelled line!!

Why is it okay for vodacom to keep robbing people when cancelling their lines? Our contracts expired on the 2nd of April but according to vodacom we have to pay for the whole of April. We tried to give notice in March but were told we cant. We gave notice on the 1st of April to terminate all lines which was 10 lines but vodacom could only locate 9 numbers. We located the 10th and called in to cancel and were ensured by the consultant that it was. Yet we have still been debited on the 1st of June. Pathetic service, We want our money back as we did our part but vodacom never seems to do theres.