Terrible service received from Vodacom after over charging me with services that I was not using.

I had an contract with Vodacom that I paid off 2018 and it kept on Billing.I called and was informed that the contract number was not cancelled.I paid the outstanding amount and now Vodacom is sending me from Pillar to post when I request for a letter of settlement or statement of account. Am in need of the above mentioned documents as it is affecting my credit score.