Vodacom reactivating old cancelled contract on their own accord and trying to collect money

I cancelled my Vodacom contract in 2018 and all billing and debit orders ceased. In 2021, Vodacom (completely on their own accord) reinstituted billing and debit orders for my contract/services cancelled in 2018 already. Neither in-store staff, Customer Care or Collections could help to resolve, merely saying that the reactivation looks "unusual" on their system. Now collections phoning me daily without any merit to say I owe Vodacom money.