Account overdue

I stopped the compact account with MultiChoice 2018 because I never needed to watch the channels. The contract I have with MultiChoice says the account is pay in advance and never in arreas, however Mulchoice has send my details to debt collectors claiming I owe R666. I asked how is that possible as the account is paid in advance no one gave me an answer. TCR debt collectors personnel keep calling and they also do not have an explanation, they saying their job is to collect money owed.

MultiChoice have failed to give an explanation on how is it that I owe them. Your assistance in this regard will be highly appreciated.