Canceled not canceled?

Can someone please advise how, after canceling my contract several months ago, receiving notice that my debit orders had been canceled as well as further statements showing a zero balance. Why am I getting calls saying my account is in arrears? How is this not something that can be done in-store or through your 'dedicated' cancelation line, which has an unbelievable waiting time? Rather, there's now a further 14days where I am unable to use my device... except for Vodacom trying to sell me further data?

After easily over 10 years of being a loyal customer, I would hate for this to be the reason I change service providers.