Vodacom contract cancelation

I have been trying to cancel a Vodacom contract for the last 2 years, I am not using it and does not want to upgrade, period. Every time I received a call for an upgrade I informed the person that I am not interested and need them to arrange cancellations of the same, with no action whatsoever. I informed my bank to stop my debit order and now I received a letter of demand because my account is in arears. This morning I again phoned 082135 and the lady informed me to try another number ***. very interesting that this number is nowhere to be seen on my monthly statement, that not all when you dial *** the first option is for you to upgrade, second option to cancel your contract but very conveniently they can not assist due to security reasons and ask you to go online, unbelievable for a company of this size to operate at this level.