Vodacom is quick to follow up to non-payments, but has no integrity in honouring promises to call paying customers back

I have a number with vodacom since 2000 and exceeded my contract period with them years ago. I called them to cancel the contract in 2020 and was told someone will contact me back because I am on the 'old system'. Multiple attempts later and my contract is still not cancelled, resulting in listing me at the credit control bureau. I do not know how else to get the contract closed. I left my new number with them for reference multiple times too, so not being able to contact me is not acceptable as an excuse either.