Cartrack threatening client

Cateack is the worst ever. No service delivery after sales. Been struggling to get contract canceled due to breach of contract due to no service delivery by Cartrack themselves. They want payment but don't want to keep to their contract. Contract was canceled. All payments stopped until their paperwork is in order and received. To date not done. This all started 8 December 2021. Accounts keep on phoning requesting payment. No payment until paperwork is done correctly. So they have the right to blacklist and threaten with blacklisting to force me to pay without correcting their paperwork. Something needs to be done about this company.