unaceptable administration Horrific service

many years ago I contracted with Vodacom for two weekender accounts.As a caterer found that the free weekend minutes ( our busy time) to be the most feasible.Cell *** and *** was allocated.I retired from the business .I had no further use(hundres of minutes banked) The contracts expired ,was on a month to month basis..I went to Game to cancel they directed me to Vodacom Cresta . I was told I can only cancel online telephonically and gave me a number..I contacted this number and was told that the services would be cancelled after a notice period of one month... I accepted that...A few months later I noticed debits still being generated against my bank account....I went back to Vodacom Cresta and to Vodashop at Randpark Ridge. I was promised that it will be investigated .still nothing ..the debits continued . My Bankers stopped it.I wrote numerous emails received reference numbers and a phone call or two..Was told they will investigate and sorted .Now getting threatening letters which in reply I refer to all my correspondence .Still nothing..Now received another final letter of demand.I do not owe them the have to reimbursed! Someone @Vodacom Help me..I am appalled