Vodacom trying to ***** money

Vodacom keep harassing me over an amount i supposedly owe BECAUSE THEY DID NOT CANCEL A MODEM AND ****LE WHEN I INSTRUCTED THEM TO DO SO. To be clear, both were past the 24 month "locked in" time so just required 30 day cancelation period. Be very weary when cancelling anything with Vodacom, they dont want to let you go and DO NOT enter into a debit order agreement, pay by manual eft, it gives you the upper hand.