Telkom does not cancel number as per written instruction

In February we went to the Telkom store at Lakeside Mall in Benoni to cancel our business telephone by giving one months notice. Documents were completed and handed in. We were also requested e-mail the documents which has been done on more than one occasion .. My business has been moved and the line is not in use . Telkom have not acted on the instructions to cancel the telephone number and continues to send bills.