Vodacom outstanding amount

I was contacted by MBD attorneys consultants in September 2021 and they told me that I have an outstanding amount with Vodacom, which when I asked what it is for I was told is a cancelation fee. I then told them that I have settled all the amounts owed by me to Vodacom and I was told by Vodacom consultants when I paid my last payment that the contract will be canceled. I also called Vodacom to confirm that indeed the contract was canceled after I settled the account a few days later, Vodacom never made me aware that there were any amounts that I needed to pay or outstanding in March 2021 when I settled the account. I was then surprised to receive an email 6 months later from MBD attorneys that I owe Vodacom a cancelation fee. I called and emailed MBD attorneys disputing any amounts that I apparently owe Vodacom and I was told that they will investigate the matter, however to date I haven't received any feedback. Please kindly assist me with this matter as now they are harassing me (MBD attorneys consultants) as they are calling me every week, when I pick up they hang up and the said amount on the statement keeps increasing every week.