Unhappy with there services

I'm disappointed in Cell C my contract ends 5 July 2023 I called them on the 2 June 2023 to in order to place a cancellation they refused saying I must call on the 5 July 2023 because they are unable to put a notice on there said because I wanted there elast debit to be on the 27 June 2023 not the 27 July 2023