Vodacom trash accounting

A letter of FINAL DEMAND sent with an amount outstanding to me on the 2019-11-01. on 2019-11-04 I paid the amount stated on this "demand". Now i am "listed" with their "attorneys" for another amount they say is the "contract amount". When you send out a letter you should do that with the FULL AMOUNT outstanidn on the account, as Vodacom combines ALL the accounts and fees into ONE ACCOUNT NUMBER. Now, all of a sudden this changed???? So they can go on that a person is now owing this and then that and then again some. Disgusting.